11. The object and methods of composite portraiture will be best explained by the following extracts from Memwies describing successive stages published in 1878, 1879 and 1881 respectively. 1. Composite portraits made by combining those of many different persons into a single result and figure. I submit to the Anthropological Institute my first results in carrying out a process that I suggested last April, 1877, in my presidential address to the Anthropological Subsection of the British Association of Plymouth in the following words. Having obtained drawings or photographs of several persons alike in most respects, but differing in minor details, what sure method is there of extracting the typical characteristic from them? I may mention a plan which had occurred both to Mr Herbert Spencer and myself, the principle of which is to assume a pose, optically the various drawings, and to accept the aggregate's result. Mr Spencer suggested to me in conversation that the drawings reduced to the same scale might be traced on separate pieces of transparent paper and secured one upon another, and then held between the eye and the light. I have attempted this with some success. My own idea was to throw faint images of the several portraits in succession upon the same sensitised photographic plate. I may add that it is perfectly easy to assume a pose optically to portraits by means of a stereoscope and that a person who is used to handle instruments will find a common double eyeglass fitted with stereoscopic lenses to be almost as effectual and firehandier than the boxes sold in shops. Mr Spencer, as he informed me, had actually devised an instrument many years ago, portraying mechanically, longitudinal, transverse and horizontal sections of heads on transparent paper intending to superimpose them and to obtain an average result by transmitted light. Since my address was published, I have caused trials to be made and have found, as a matter of fact, that the photographic process of which I there spoke enables us to maintain, with mechanical position, a generalised picture, one that represents no man in particular but portrays an imaginary figure possessing the average features of any given group of men. These ideal faces have a surprising area of reality. Nobody who glanced at one of them for the first time would doubt its being the likeness of a living person. Yet, as I have said, there is no such thing. It is a portrait of a type and not of an individual. I begin by collecting photographs of the persons with whom I propose to deal. They must be similar in attitude and size, but no exactness is necessary in either of these respects. Then, by simple contrivance, I make two pinholes in each of them to enable me to hang them up in front of the other like a pack of cards upon the same pair of pins in such a way that the eyes of all the portraits shall be as nearly as possible superimposed. In which case the remainder of the features will also be superimposed nearly enough. These pinholes correspond to what are technically known to printers as register marks. They are easily made. A slip of brass or card has an aperture cut out of its middle and threads are stretched on opposite sides making a cross. Two small holes are drilled in the plate, one on either side of the aperture. The slip of brass is laid on the portrait with the aperture over its face. It is turned about until one of the cross threads cuts the pupils of both eyes and is further adjusted until the other thread divides the interval between the pupils into equal parts. Then it is held firmly and a prick is made through each of the holes. The portraits being thus arranged, a photographic camera, is directed upon them. Suppose there are eight portraits in the pack and that under existing circumstances it would require an exposure of 80 seconds to give an exact photographic copy of any one of them. The general principle of preceding is this, subject in practice to some variations of detail depending on the different brightness of the several portraits. We throw the image of each of the eight portraits into and upon the same part of the sensitised plate for 10 seconds. Thus, portrait number one is in the front of the pack. We take the cap off the object glass, the camera for 10 seconds and afterwards replace it. We then remove number one from the pins. Number two appears in the front. We take off the cap a second time for 10 seconds and again replace it. Next we remove number two and number three appears in the front which we treat as its predecessors and so we go on to the last of the pack. The sensitised plate we now have as its total exposure of 80 seconds is then developed and the print taken from it is the generalised picture of which I speak. It is a composite of eight component portraits. Those without lines are sharpest and darkest that are common to the lightest number of the components and purely individual peculiarities leave little and no visible trace. The latter being necessarily deposed equally on both sides of the average and outline of the composite is the average of all the components. It is a band not a fine line because the outlines of the components are seldom exactly superimposed. The band will be darkest in its middle whenever the component portraits have the same general type of features and its breadth or amount of blur will measure the tendency of the components to deviate from the common type. This is so for the very same reason that the dot shot marks on a target are more thickly disposed in the bull's eye than away from it and at a greater degree as the marksmen are more skillful. All that has been said of the outlines is equally true as regards to shadows. The result being that the composite represents an average figure whose linements have been softly drawn. The eyes come out with appropriate distinctness to the mechanical conditions under which the components were hung. A composite portrait represents the picture that would rise before the mind's eye of a man who had the gift of pictorial imagination in an exalted degree. By the imaginative power even of the highest artist is far from precise and is so apt to be biased by special cases that may have stuck their fancies that no two artists agree in any of their typical forms. The merit of the photographic composite is its mechanical position being subject to no errors beyond those incidental to all photographic productions. I submit several composites made for me by Mr. H. Reynolds. The first set of portraits are those of criminals convicted of murder, manslaughter or robbery accompanied with violence. It will be observed that the features of the composites are much better looking than those of the components. The special villainous irregularities in the latter have disappeared and the common humanity that analyzed them has prevailed. They represent not the criminal but the man who was liable to fall into crime. All composites are better looking than their components because the average portrait of many persons is free from irregularities that previously blemish looks of each of them. I selected these for my first trials because I happened to possess a large collection of photographs of criminals through the kindness of Sir Edmund Ducan, the director general of prisons under the purpose of investigating criminal types. They were particularly adapted to my present purpose, being all made of about the same size, taking in much the same attitudes as was endeavouring to us as the principal criminal types by methods of optical superimposition of the portraits, such as I frequently employed with maps and metrological traces that the idea of composite figures first occurred to me. The other set of composites are made from pairs of components. They are selected to show the extraordinary facility of combining almost two faces with proportions are in any way similar. I will, I am sure, surprise most persons to see how well defined these composites are. Then we deal with faces of the same type. The points of similarity fire at a number of those of dissimilarity. There is a much greater resemblance between faces generally than we will turn our attention to individual differences I rap to appreciate. I travel on his first arrival among people of a race very different to his own. Thanks to them closely alike. And a Hindu has much difficulty in distinguishing one Englishman from another. The fairness with which photographic composites represent their components is shown by six of the specimens. I wish to learn whether the order in which the components were photographed made any material difference in the result. So I had three of the portraits arranged successively in each of their six possible combinations. It will be observed that four, at least of the six composites are closely alike. I should say that in each of this set, which was made by the wet process, the last of three components was always allowed a longer exposure. Then the second, and the second and the first. But it is found better to allow an equal time to all of them. There is a picture indicated in the middle of the page with accompanying text. The accompanying woodcut is a fair representation of one of the composites as is practical in ordinary printing. It was photographically transferred to the wood and the engraver has used his best endeavour to translate the shades into line engraving. This composite is made out of only three components, but its three-fold origin is to be traced in use and in the buttons to the vest. To the vest of my judgement, the original photograph is a very exact average of its components. Not one feature in it appears identical with that of any one of them. But it contains a resemblance to all and is not more like to one of them than to another. However, the judgement of the wood engraver is different. His rendering of the composite has made it exactly like one of its components, which it must be borne in mind he had never seen. It is just as though an artist drawing a child had produced a portrait closely resembling its deceased father, having overlooked an equally strong likeness to his deceased mother, which was apparent to its relatives. This is to me my striking proof that the composite is a true combination. The stereoscope, as I stated last August in my address at Plymouth, affords a very easy method of optically superimposing two portraits. And I have much pleasure in quoting the following letter, pointing out this fact as well as some other conclusions to which I also had arrived. The letter was kindly forwarded to me by Mr Darwin. It is dated last November and was written to him by Mr A. L. Austin from New Zealand, thus affording another of the many curious incidences of two persons being independently engaged in the same novel and quarry and nearly at the same time and coming to similar results. Info Cargill, New Zealand, November 6, 1877 To Charles Darwin, Esquire Sir, although a perfect stranger to you and living on the reverse side of the globe, I have taken the liberty of writing to you on a small discovery I have made in binocular vision in the stereoscope. I find by taking two ordinary, courage-devisit photos of two different persons' faces, the portraits being about the same size and looking about the same direction and placing them in a stereoscope, the faces blended to one in a most remarkable manner, reducing the case of some ladies' portraits in every instance a decided improvement in beauty. The pictures were not taken in a binocular camera and therefore did not stand out well. But, by moving one of both until the eyes coincide in the stereoscope, the pictures blend perfectly. If taken in a binocular camera, for the purpose, each person being taken on one half of the negative, I'm sure the results would be more striking. Perhaps something might be made of this in regard to the expression of emotions in man and the lower animals, etc. I have not time or opportunities to make experiments, but it seems to me something might be made of this by photographing the faces of different animals, producing races of mankind, etc. I think a stereoscopic view of one of the ape, tribe and some low-class human face would make a very curious mixture, also in the matter of crossing of animals and the resulting offspring. It seems to me something also might result in photos of husband and wife and children, etc. In any case, the results are curious. If it leads to nothing else, should this come to anything, you will know to acknowledge myself as suggesting the experiment and perhaps send me some of the results. If not likely to come to anything, a reply would much oblige me. It was very truly A. L. Austin C. E. F. R. A. S. Dr. Carbadan reports me that the late Mr. Repould, the Mechanican, used to combine two portraits of himself under the stereoscope, the one had been taken with an assumed stern expression, the other with a smile, and his combination produced a curious feeling of the two. Convenient as a stereoscope is owing to its accessibility for determining whether any two portraits are suitable in size and attitude to form a good composite, is nevertheless a makeshift and imperfect way of attaining the required result. It cannot of itself combine two images, it can only place them so that the office of attempting to combine them may be undertaken by the brain. Now the two separate impressions received by the brain through the stereoscope do not seem to me to be relatively constant in their vividness, but sometimes the image seen by the left eye prevails over that scene by the right and vice versa. All the other instruments I'm about to describe accomplish that which the stereoscope fails to do. They create true optical combinations. As regards other points in Mr. Austin's letters, I cannot think of the use of a binocular camera for making the two portraits intended to be combined into one by the stereoscope would be of importance. All that is wanted is that the portraits should be nearly of the same size. In every other respect I cordially agree with Mr. Austin. The best instrument I have is yet contrived and used for optical superimposition is a double image prism of Iceland's spy Seatfigure page 228. Formerly procured for me by the late Mr. Tisley Optician Brompton Road. They have a clear aperture of a square half an inch on the side and held at right angles to the line of sight will separate the ordinary and extraordinary images to the amount of two inches when the object viewed is held at 17 inches from the eye. This is quite sufficient for working with character-divisit portraits. One image is quite a chromatic. The other shows little colour. The divergence may be varied and adjusted by inclining the prism to the line of sight. By its means the ordinary image of one component is thrown upon the extraordinary image of the other and the composite may be viewed by the naked eye or through a lens of long focus or through an opera glass and telescope is not so good. Fitted with a sufficiently long draw tube to see an object at that short distance with distinctness. Portraits of somewhat different sizes may be combined by placing the larger one farther from the eye and a long face may be fitted to a short one by inclining and foreshortening the former. The slight fold of focus thereby occasionally produces little sensibly ill effect on the appearance of the composite. The front or the profile faces of two living persons sitting side by side or one behind the other can be easily superimposed by double inch prism. Two such prisms set one behind the other can be made to give four images of equal brightness occupying the four corners of a rhombus whose acute angles are 450. Three prisms will give eight images but this is practically not a good combination. These fail in distinctness and are too near together for use. Again each lens of a stereo scope of long focus can have one or a pair of these prisms attached to it and four or eight images may be thus combined. Another instrument I have made consists of a piece of glass inclined at a very acute angle to the line of sight and of a mirror beyond it also inclined but in the opposite direction to the line of sight. Figure one is displayed on the previous page. Figure one shows the simple apparatus which carries a prism on which the photograph is mounted. The former is set in a round box which can be rotated in the ring at the end of the arm and can be clamped when adjusted. The arm can be rotated and can also be pulled out or in if desired and clamped. The floor of the instrument is overlaid with cork covered with black cloth on which the components can easily be fixed by drawing pins. When using it, one portrait is pinned down and the other is moved near it overlapping its margin if necessary until the eye looking through the prism sees a required combination then the second portrait is pinned down also. It may now receive its register marks from needles fixed in a hinged arm and this is a more general applicable method and a plan with cross threads already described as an inter-side feature. The nose, the ear or the hand may thus be selected for composite purposes. Let A, B, C, Y, Z be the components. A is pinned down and B, C, Y, Z are successfully combined with A and registered. Then before removing Z, take away A and substitute any other of the already registered portraits. Say A by combining it with Z. Lastly remove Z and substitute A by combining it with A and register it. Figure 2 shows one of three similarly jointed arms which clamp on to the vertical rod. Two of these carry a light frame covered with cork and cloth and the other carries figure 3 which is a frame having lenses of different powers set into it and on which or on the third frame a small mirror incline of 150 may be laid. When a portrait requires foreshortening it can be pinned on one of these frames and be inclined to the light of sight. When it is smaller than its fellow it can be nearer to the eye and an appropriate lens interposed. When a right side of profile has to be combined with a left-hand one it must be pinned on one of the frames interviewed by reflection from the mirror in the other. The apparatus I have drawn is roughly made and being chiefly of wood is rather clumsy but it acts well. Two rays of light will therefore reach the eye from each point of the glass. The one has been reflected from its surface and the other has been first reflected from the mirror and then transmitted through the glass. The glass used should be extremely thin to avoid the blur due to double reflections. It may be a selected piece from those made to cover microscopic specimens. The principle of the instrument may be yet further developed by interposing additional pieces of glass, successively less inclined to the line of sight and each reflecting a different portrait. I have tried many other plans, indeed the possible methods of optically superimposing in two or more images are very numerous. Thus I have used a sextant with its telescope attached, also strips of mirrors placed at different angles. There are several reflections being simultaneously viewed through a telescope. I have also used a divided lens like two stereoscopic lenses all close together in front of the object glass of a telescope. Two generic images extract from proceedings Royal Institution 23 April 1879. Our general impressions are founded upon blended memories, and this letter will be the chief topic of the present discourse. An analogy will be ported out between these and the blended portraits first described by myself a year ago under the name of composite portraits, and specimens of the letter will be exhibited. The physiological basis of memory is simple enough in its broad outlines. Whenever any group of brain elements has been excited by a sense of impression it becomes so to speak, tender and liable to be easily thrown again into a similar state of excitement. If the new cause of excitement differs from the original one a memory is the result. Whenever a single cause throws different groups of brain elements simultaneously into excitement, the result must be a blended memory. We are familiar with the fact that faint memories are very apt to become confused. There are some picture of mountain and lake in a country which we have never visited often recalls a very sense of identity with much we have seen elsewhere. Our recollections cannot be disentangled though general resemblances are recognised. It is also a fact that the memories of persons who have great powers of visualising, that is of seen world of fine images in the mind's eye, are no less capable of being blended together. Artists are, as a class possessed of the visualising power in a high degree, and they are at the same time the amnesty distinguished by their gifts of generalisation. They are, of all men, the most capable of producing forms that are not copies of any individual but represent the characteristic features of classes. There is then no doubt from whatever side the subject of memory is approached, whether from the material or from the mental and in the latter case, whether we examine the experiences of those in whom the visualising faculty is faint or in whom it is strong that the brain has the capacity of blending memories together. Neither can there be any doubt the general impressions are faint and perhaps faulty additions of blended memories. They are subject to errors of their own and they inherit all those to which the memories are themselves liable. Specimens of blended portraits will now be exhibited. These might, with more propriety, be named according to the happy phrase Professor Huxley, generic portraits. The word generic presupposes a genius. That is to say, a collection of individuals who have much in common, and among whose meaning and characteristics are very much more frequent than extreme ones. The same idea is somehow expressed by the word typical, which was much used by Quitalit, who was the first to give it a rigorous interpretation and whose idea of a type lies at the basis of his statistical views. No statistic in dreams of combining objects into the same generic group then do not cluster towards a common center. No more should we attempt to compose generic portraits out of heterogenic elements, for if we do so, the result is monstrous and meaningless. It might be expected that when many different portraits are fused into a single one, the result will be a mere smudge. Such, however, is by no means a case. Out of the conditions just laid down of a great profilance of the mediocre characteristics of the extreme ones, there are then so many traits in common to combine and to reinforce one another that they prevail to the exclusion of the rest. All that is common remains. All that is individual tends to disappear. The first of the composites exhibited on this occasion is made by conveying the images of three separate portraits by means of three separate magic lanterns upon the same scene. The stance on which the lanterns are mounted have been arranged to allow of nice adjustment. The composite about to be shown is one that drains the powers of the process somewhat too severely. Their portraits combined being those of two brothers and their sister, who have not even been photographed in precisely the same attitudes. Nevertheless, the result is seen to be the production of a face, neither male nor female, but more regular and handsome than any other component portraits and in which the common family traits are clearly marked. Ghosts of portraits of male and female attire due to their peculiarities of the separate portraits are seen about to turn around the composite, but they are not sufficiently vivid to distract the attention. If the number of combined portraits had been large, these ghostly accessories would have become too faint to be visible. The next step is to combine this portrait of two brothers and their sister, which has been composed by optical means before the eyes of the audience and concerning the truthfulness of which there can be no doubt with a photographic composite of the same group. The letter is now placed in a fourth magic lantern with a buttered light behind it and as the image is thrown on the screen by the side of the composite produced by direct optical superposition. It will be observed that the two processes lead to almost exactly the same result and therefore the fairness of the photographic process may be taken for granted. However, two other comparisons will be made for the sake of verification, namely between the optical and photographic composites of two children and a game of two brothers, Contadini. The composite portraits that will next be exhibited are made by the photographic process and it will now be understood that they are truly composite, notwithstanding their definition and apparent individuality. Attention is however first directed to a convenient instrument not more than 18 inches in length, which is in fact a photographic camera with six converging lenses and an attached screen on which six pictures can be adjusted and brilliantly illuminated by artificial light. The effect of their optical combination can thus be easily studied. Any errors of adjustment can be rectified and the composite may be photographed at once. It must not be supposed that any one of the components fails to leave its due trace in the photographic composite, much less in the optical one. In order to align misgivings on the subject a small apparatus is laid on the table together with some of the results obtained by it. Here's a cardboard frame with a spring shutter closing an aperture of the size of a weaver that springs open on the pressure of a finger and shuts again as settling when the pressure is withdrawn. A chronograph is held in the other hand whose index begins to travel at the moment the finger presses a spring and stops instantly on lifting the finger. The two instruments are worked simultaneously. The chronograph checking time allowed for each exposure and summing all the others. It appears from several trials that the effect of 1,000 brief exposures is practically identical to that of a single exposure of 1,000 times the duration of any one of them. Therefore, each of a thousand components leaves its due photographic trace on the composite, though it is far too faint to be visible unless reinforced by many similar traces. The composites now to be exhibited are made from coins or metals the aim has been to obtain the best likeness obtainable of historical personages by compiling various portraits of them taking a different period of their lives and so to elicit the traits that are common to each series. A few of the individual portraits are placed in the same side with each composite to give a better idea of the character of these blended representatives. Those that are shown are 1. Alexander the Great from 6 components 2. Antiochus King of Syria from 6 3. Demetrius Polyocritus from 6 4. Cleopatra from 5 Here the composite is as usual better looking than any of the components none of which however give any indication of her reputed beauty in fact her features are not only plain but to an ordinary English taste are simply hideous 5. Nero from 11 6. A combination of 5 different Greek female faces and 7 a singularly beautiful combination of the faces of 6 different Roman ladies forming a charming ideal profile My accordio acknowledgement is due to Mr. Iris Stewart Poole the learner curator of the coins and gems the British Museum for his kind selection of the most suitable medals and for procuring casts of them for the present purpose These casts were with one exception all photographed to a uniform size of an inch between the pupils of the eyes and the division between the lips which experience shows to be the most convenient size on the whole to work with, regard being paid to many considerations not worthwhile to specify in detail When it wasn't necessary the photograph was reversed, these photographs were made by Mr. H Reynolds I then adjusted and repaired them for taking the photographic composite The next series to be exhibited consists of composites taken from the portraits of H Reynolds, Confected of Murder, Mansourdo or Crimes Accompanied by Violence There is much interest in the fact that two types of features are found much more frequently among these than among the population at large In one the features are broad and massive like those of Henry VIII but with a much smaller brain The other of which 5 composites are exhibited each deduced from a number of different individuals varying 4 to 9 is a face that is weak and certainly not a common English face 3 of these composites are taken from entirely different sets of individuals or as alike as brothers and is found on optically combining any 3 out of the 5 composites that is on combining almost any considerable number of the individuals the result is closely the same The combination of the 3 closely alluded to will now be affected by means of the 3 converging magic lanterns and the result may be accepted a generic in respect of this particular type of criminals The process of composite portraiture is one of pictorial statistics It is a familiar fact that the average height of even a dozen men of the same race taking at hazard varies so little that for ordinary statistical purposes it may be considered constant the same may be said of the measurement of every separate feature in them and of every tint whether of skin, hair or eyes Consequently a pictorial combination of any one of these separate traits would lead to results done less constant than the statistical averages In a portrait there is another factor to be considered the size, the measurement of the separate traits namely their relative position but these two in a sufficiently large group would necessarily have a statistical constancy As a matter of observation the resemblance between persons of the same genus in the same sense of generica as already explained is efficiently great to admit of making good pictorial composites out of even small groups as has been abundantly shown composite pictures are however much more than averages they are rather the equivalence of those large statistical tables whose totals divided by the number of cases and entered in the bottom line are the averages they are real generalizations because they include the whole of the material under consideration the blur of their outlines which is never great in truly generic composites except in unimportant details matches the tendency of individuals to deviate from the central type my argument is that the generic images that arise before the mind's eye and the general impressions which are faint and faulty additions of them are the analogs of these composite pictures which we have the advantage of examining a leisure and whose peculiarities and character we can investigate and from which we may draw conclusions that shall show much light on the nature of certain mental processes which are too mobile and evanescent to be directly dealt with right before the photographic society 24th of June 1881 I propose to draw attention to NIGHT to the results of recent experiments and considerable improvements in a process of which I published the principles three years ago and which I have subsequently exhibited more than once I have shown that if we have the portraits of two or more different persons taken in the same aspect and under the same conditions of light and shade and that if we put them into different optical lanterns converging on the same screen and carefully adjust them first so as to bring them to the same scale and secondly so as to superimpose them as accurately as conditions admit then the different phases will blend surprisingly well into a single countenance if they are not very dissimilar the blender result will always have a curious area of individuality and will be unexpectedly well defined it will exactly resemble none of its components but it will have a sort of family of likeness to all of them and it will be an ideal and an average portrait I have also shown that the image on the screen might be photographed then and there or that the same result may be much more easily obtained by a method of successive photography and I have exhibited many specimens made on this principle photolithographs of some of those we found in the proceedings by the Royal Institution as illustrations of a lecture I gave there on generic images in 1879 the method I now use is much better than those previously described it leads to more accurate results and is easier to manage I will exhibit and explain the apparatus as it stands and will indicate some improvements as I go on the apparatus is here I use it by guest light and employ rapid dry plates which however, under the conditions of a particularly small aperture and the character of the light require 60 seconds of total exposure the apparatus is 4 feet long and 6.5 inches broad it lies with its side along the edge of the table at which I sit and it is sloped towards me so that by bending my neck slightly I can bring my eye to the eye hole where I watch the effect of the adjustments which my hands are free to make the entire management of the whole of this is within an easy arms length and I complete the process without shifting my seat the apparatus consists of 3 parts A, B and C A is rigidly fixed on the dark side of the contravences by which the position of the image can be viewed the eye hole already mentioned being part of A B is a travelling carriage that holds the lens as connected by Bellow's work with A my apparatus is pushed out and in and clamped where desired but it ought to be moved altogether by pinion and rackwork the lens I use is A, I, B down my air its focal length is appropriate to the size of the instrument and I find great convenience in a lens of wide aperture when making the adjustments as I then require plenty of light but as to the photography the smaller the aperture the better the hole in my stop is only two tenths of an inch in diameter and I believe one tenth will be more suitable C is a travelling carriage that supports the portraits in turn by which the composite has to be made I work directly from the original negatives with transmitted light but prints can be used with light falling on their face an image is displayed on the previous page with the side view and end view of the apparatus for convenience of description I will confine myself to the first instance only and will therefore speak of C as a carriage that supports the frame that holds the negative transparencies C can be pushed along the board and be clamped anywhere and it has a rack and pinion adjustment but it should have been made movable by a rack and pinion along the whole length of the board the frame for the transparencies has the same movement of adjustment as those in the stage of a microscope it rotates around a hollow axis through which the beam of light is thrown and independent movements in the plane add right angles to the axis can be given to it in two directions add right angles to one another by turning two separate screws the beam of light is furnished by three gas burners and it passes through a condenser the gas is supplied through a flexible tube that does not interfere with the movements of C and is governed by a stopcock in front of the operator the apparatus so far as it has been described with any detail at ignoring what was said about an eyehole is little else than a modified copy and camera by which an image of the transparency could be thrown on the ordinary focusing screen and be altered in scale and position until it was adjusted to verduceal lines drawn on the screen it is conceivable that this should be done and that the screen should be replaced by the dark side and a brief exposure given to the plate then at a fresh transparency should be inserted a fresh focus the adjustment made and a second exposure given and so on this I say is conceivable but it would be very inconvenient the adjusting screws would be out of reach the head of the operator would be in an awkward position and though these two difficulties might be overcome in some degree a serious risk of an occasional shift to the plate during the frequent replacement of the dark slide would remain I avoid all this by making my adjustments while the plate continues in position with its front open I do so through the help of a reflector temporarily interposed between it and the lens I do not use the ordinary focusing screen at all in making my adjustments but one that is flush or nearly so with the roof of the camera when the reflector is interposed the image is wholly cut off from the sensitized plate and it's thrown upwards against this focusing screen when the reflector is drawn the image falls on the plate it is upon this focusing screen in the roof that I see the fiducio lines by which I make all the adjustments nothing can be more convenient than the position of this focusing screen for working purposes I look down on the image as I do upon a book resting on a sleeping desk and all the parts of the apparatus are within an easy arms length my reflector in my present instrument is I am a little ashamed to confess nothing better than a piece of looking glass fixed to an axle within the camera near its top left hand edge on the end of the axle protrudes and as a short arm when I push the arm back the mirror is raised when I push it forward it drops down I use the swing glass because the swing action is very true and as my apparatus was merely a provisional working model made of soft wood I did not like to use sliding arrangements which might not have acted truly or I should certainly have a slight with a rectangular glass prism on account of the perfect reflection of the forwards and let me say that a prism of two inches square in the side is quite large enough for adjustment purposes for it is only the face of the portrait that is wanted to be seen I chose my looking glass carefully and selected a piece that was plain and parallel it has not too high a polish and therefore does not give troublesome double reflections in fact it answers very respectively especially when we consider the direction of definition is thrown away on composites I thought of a mirror silvered on the front of the glass but this would soon tarnish in the gas light so it did not try it but certainly against the emission of light unintentionally I ever kept the focusing screen of the roof and a slide in the fixed body instrument immediately behind the reflector and before the dark slide neither of these we wanted the reflector was replaced by prism set into one end of a sliding block that had a large horizontal hole at the other end I also positioned length of solid wood between the two to block out the passive light both upwards and downwards whenever the block is passing through the halfway position as regards the do-see-your lines they might be drawn on the glass screen but black lines are not I find the best it is far easier to work with illuminated lines and it is important to be able to control their brightness I produced these lines by means of a vertical transparency set in an adjustable frame connected with A gas light behind it below the eye hole he through which I view the glass screen G it is a thin piece of glass set at an angle of 450 which reflects the do-see-your lines and gives them the appearance of lying on the screen the frame being so adjusted that the distance from the thin piece of glass to the transparency and to the glass screen G is the same I thus obtain beautiful do-see-your lines which I can vary from extreme fairness to extreme brilliancy by turning the gas lower or higher according to the brightness of the image of the portrait which itself depends on the density of the transparency that I am engaged upon this arrangement seems as good as can be it affords a gauge of the density of the negative and enables me to regulate the burners behind it until the image of the portrait on G is adjusted to a standard degree of brightness for conveyance and enlarging or reducing I take care that the intersection of the vertical do-see-your line which passes through the pupils of the eyes shall correspond to the optical access of the camera then as I enlarge or reduce that point in the image remains fixed the uppermost horizontal do-see-your line continues to intersect the pupils and the vertical one continues to divide the face symmetrically the mouth has a loan to be watched when the mouth is adjusted to the lower do-see-your line the scale is exact it is a great help having to attend no more than one varying element the only inconvenience is that the image does not lie in the best position on the plate when the point between the eyes occupies its centre this is easily remedied by using a larger back with a suitable inner frame I have a more elaborate contrivance in my apparatus to produce the same result which I need not stop to explain for success and speed in making composites the apparatus should be solidly made chiefly of metal and all the adjustments ought to work smoothly and accurately good composites cannot be made without very careful adjustment in scale and position, an offhand way of working produces nothing but failures I will first exhibit a very simple but instructive composite effect I draw on a square card a circle of about 2.5 inches in diameter and two cross lines for its centre cutting one another at right angles round each of the four points 900 apart, where the cross cuts a circle I drew small circles of the sides of wafers and gummed upon each a disc of different tint finally I made a single black dot halfway between two of the arms of the cross I then made a composite of the four positions of the card as it was placed successfully which each of its sides downwards the result is a photograph having a sharply defined cross surrounded by four discs of precisely uniform tint and between each pair of arms of the cross there is a very faint dot this photograph shows many things the effect of it being a composite is shown by the four faint dots the equality of the successive periods of exposure is shown by the equal tint to the four dots the accuracy of the adjustment is shown by the sharpness of the cross being as great in the composite as in the original card we see the smallest of the effect produced by any trait such as the dot when it appears in the same place in only one of the composites if this effect be so small in a series of only four components it would certainly be imperceptible in a much larger series thirdly the uniformity of resulting tint in the composite wafer is quite irrespective of the order of exposure there are four components waivers A, B, C, D respectively and the four composite waivers 1, 2, 3, 4, then we will see by the diagram that the order of exposure has differed in each case yet the result is identical therefore the order of exposure has no effect on the results a table is displayed on the page with composite and successive places of components I will next show a series consisting of two portraits considerably unlike to one another so very discordant as to refuse to conform and of two intermediate composites in making one of the composites I gave two thirds of the total time of exposure to the first portrait and one third to the second portrait in making the other composite I did the converse it will be seen how good its results in both cases and how the likeness of the longest exposed portrait always predominates the next in a series of four composites first consists of 57 hospital patients suffering under one or other of the many forms of consumption I may say that with the aid of Dr. Mahomet I am endeavoring to utilize this process to elicit the physiognomy of disease the composite I now show is what I call a hodgepodge composite its use is to form a standard when deviations towards any particular subtype may be conveniently gauged it will be observed that the face is strongly marked and that it is quite idealised I claim for composite portraiture that it affords a method of obtaining pictorial averages which affects simultaneously for every point in a picture what a method of numerical averages would do for each point in the picture separately it gives in short the average tint of each unit of area in the picture measured from judicial lines as coordinates now every statistic knows by experience the numerical averages usually begin to agree pretty fairly when we deal with even 20 or 30 cases therefore we should expect to find that any groups of 20 or 30 men of the same class would yield composites bearing a considerable likeness to one another improve of this is the case I exhibit three other composites the one is marked from the first 20 portraits of the 57 the second from the last 27 and the third is made on 36 portraits taken indiscriminately out of all 57 it will be observed that all composites are closely like I will now show a few typical portraits I selected of 82 male portraits of a different series of consumptive male patients there were those that had more or less of a particular one look than I wished to visit the selected cases were about 18 in number and from these I took 12 ejecting about 6 as having some marked peculiarity that did not conform well with the remaining 12 the result is a very striking face though the ideal and artistic of the beautiful is indeed most notable how beautiful all composites are individual peculiarities all irregularities and the composite is always regular I show a composite of 15 female faces also of consumptive patients they give somewhat the same aspect of the disease also 2 others are only 6 in each and have in consequence less of an ideal look but which are still typical I have here several other typical faces in my collection of composites they are all serviceable as illustrations of this memoir but medically speaking they are only provisional results I am indebted to Lieutenant Lennot Darwin I read for an interesting series of negatives of officers and privates of the Royal Engineers here is a compositor of 12 officers here is one of 30 privates I then thought it better to select from the latter the men that came from the southern countries and again make a first selection of one from these on the principle already explained here is the result it is very interesting to note there is a damp of culture and refinement on the compositive officer and the honest and vigorous but more homely features of the privates the combination of these two officers and privates together gets a very effective physiognomy let me borne in mind that existing characters the visit are almost certain to be useless among dozens of them it is hard to find 3 that fulfil the conditions of similarity of aspect of the shade the videos have to be made on purpose I use a repeating back and a quarter plate and get 2 good sized heads on each plate and of a scale that never gives less than 4 tenths of an inch between the pupils of the eyes and the mouth it is only the head that can be used has more distant parts even used become blurred hopelessly it will be asked of what use can all this be to ordinary photographers even granting that it may be of scientific value in ethnological research that applies into the physiognomy of disease and for other special purposes I think it can be turned the most interesting account in the production of family likenesses the most unartistic productions of amateur photography do quite as well for making composites as those of the best professional workers because their blemishes vanish in the blended result all that amateurs have to do is to take negatives of the various members of their families in precisely the same aspect one recommend either perfect full face or perfect profile and under precisely the same conditions of light and shade and to send them to a firm provided with proper instrumental appliances to make composites form them the result is sure to be artistic and expression and flatteringly handsome and will be very interesting to the members of the family young and mid old and persons of both sexes can be combined into one ideal face I can well imagine a fashion setting to have these pictures professional skill might be exercised very effectively in retouching composites it would be easy to obliterate the ghost of stray features that are always present from the composites made from only a few portraits and it would not be difficult to tone down any regularity in the features themselves due to some unconstructed peculiarity in one of the components a higher order of artistic skill might be well bestowed upon the composites that have been made out of a large number of components here the regularities disappear the features are perfectly regular and idealised but the result is dim it's like a pencil drawing where many attempts have been made to obtain the desired effect such a drawing is smudged and ineffective but the artist, Andrew Skidens draws his final work with clear bold touches and then he rubs after smudge on precisely the same principle the faint but beautifully idealised features of the composites are, I believe capable of forming the basis of a very high order of artistic work End of Appendix Part 1 End of Section 11 Section 12 Appendix Part 2 of Enquirer to Human Faculty in its developments by Francis Galton This is the LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Recorded by Leon Harvey Appendix Part 2 B The relative supplies from town and country families to the population of future generations read before the Statistical Society in 1873 It is well known that the population of towns decays and has to be recruited by immigrants from the country but I am not aware that any statistical investigation has yet been attempted of the rate of its decay The more energetic members of our race who's breed is the most valuable to our nation are attracted from the country to our towns if residents in towns seriously interfere with the maintenance of their stock they would expect the breed of Englishmen to steadily deteriorate as far as that particular influence is concerned I am well aware that the only perfectly trustworthy way of conducting the inquiry is by statistics derived from numerous life histories but I find it very difficult to procure these data I therefore have had recourse to an indirect method based on a selection from the returns made at the census of 1871 which appears calculated to give a fair approximation to the truth My object is to find the number of adult male representatives in this generation of 1,000 adult males in the previous one of rural and urban populations respectively the principle in which I have proceeded is this I find A, the number of children of equal numbers of urban and rural mothers the census schedules contains records of the names and averages of the members of each family by which word we are to understand those members who are alive and resident in the same house with their parents when the mothers are young the children are necessarily very young and nearly always in at least those classes who are unable to send their children to boarding schools live at home if therefore we limit our inquiries to the census families of young mothers the results may be accepted as practically identical but we had direct means of ascertaining the number of their living children the limits of age of the mothers which I adopted in my selection were 24 and 40 years and I begin to work afresh I should prefer the period from 20 to 35 but I reason to feel pretty well contented with my present data I correct the results thus far obtained on the following grounds B, the relative mortality of the two classes between childhood and maturity C, the relative mortality of the rural and urban mothers during childbearing ages D, the relative celibacy and E, the span of a rural and rural generation it will be shown that B is important and C is not worthy but that D and E may be disregarded in deciding on the districts to be investigated it was important to choose well marked specimens of urban and rural populations in the former a town was wanted where there were various industries and where the population was not increasing a town where only one industry was pursued will not be a fair sample because the particular industry might be suspected of having a special influence and a town that was increasing would have attracted numerous immigrants from the country who are undistinguishable as such in census returns Guided by these considerations I selected Coventry where silk weaving, watchmaking and other industries are carried on and whose population had scarcely arrived to the 1871 it is an open town in which the crowded alleys of larger places are not frequent its urban peculiarities are therefore minimized and its statistical returns would give a picture somewhat too favourable of the average condition of life in towns for specimens of rural districts I chose small agricultural parishes in Warwickshire by the court's permission of Dr Farre I was enabled to procure extracts from the census returns concerning families of factory hands at Coventry in which the age of the mother was neither less than 24 nor more than 40 years and concerning another 1,000 families of agricultural labourers in rural parishes of Warwickshire under the same limitations as to the age of the mother when these returns were classified See Table 1, page 246 I found the figures to run in such regular sequence as to make it certain that the cases were sufficiently numerous to give trustworthy results it appeared that the 1,000 families of factory hands comprised 2,681 children and the 1,000 of agricultural labourers comprised 2,911 hence the children of the urban families the mothers being between the ages of 24 and 40 are on the whole about 8% less numerous than the rural I see no reason why these numbers should not be accepted as relatively correct for families and the ordinary sense of the word and for mothers of all ages an inspection of the table does indeed show that if the selection had begun at an earlier age at 24 there would have been an increased proportion of sterile and small families among the factory hands but not sufficient to introduce any substantial modifications of the above results it is however important to recollect that the small error, whatever its amount may be is a concession in favour of the towns B there is no allowance for the mortality between childhood and maturity which will diminish the above figures in different proportions because the conditions of town life are more fatal to children than those of the country no life tables exist for coventry and warwick shire I am therefore obliged to use statistics for similar condition localities to determine the amount of the allowance that should be made the life tables of Manchester will afford the date of the towns and those of the healthy districts in the country by applying these we would calculate the number of the children of ages specified for the sense of returns that would attain maturity I regret extremely that when I had the copies taken I did not give instructions to have the ages of all the children inserted but I did not and it is too late now to remedy the admission I am therefore obliged to make a very rough but not an unfair estimate the average age of the children was about 3 years and 25 years may be taken now it will be found that 74% of children in Manchester at the age of 3 reached the age of 25 while 86% of children do so in the healthy districts therefore if my rough method be accepted as approximately fair the number of adults who will be derived from the children of the 1000 factory families should be reckoned at 2681 multiplied by 74 divided by 100 equals 1986 and those from the 1000 agricultural at 2,911 multiplied by 86 divided by 100 equals 2,503 see the comparison we seek is between the total families produced by an equal number of urban and rural women who had survived the age of 24 many of these women will not marry at all I postpone that consideration to the next paragraph many of the rest will die before they reach the age of 40 and more of them will die in the town and in the country it appears from data furnished by the above mentioned tables that if 100 women of the age of 24 had annually been added to a population the number of those so added living between the ages of 2440 and interval of 17 years would be 1539 under the conditions of life in Manchester and 1585 under those the healthy districts therefore the small factors to be applied respectively to the two cases on account of this correction are 1539 divided by 17 multiplied by 100 and 1585 divided by 17 multiplied by 100 D I have no trustworthy data for the relative prevalence of celibacy in town and country all that I have learned from the census returns is that when searching them for the 1,000 families 131 bachelors were noted between the ages of 2440 among the factory hands and 144 among the agricultural laborers these figures be accepted as correct guides to the amount of celibacy among the women it would follow that I must be considered to have discussed the cases of 1,131 factory and 1,144 agricultural women when dealing with those of 1,000 mothers near the class consequently that the respective corrections to be applied are given by the factors 1000 divided by 1131 and 1000 divided by 1141 or 88.4 divided by 1,087 divided by 1,000 this difference of less than 1% is hardly worth applying moreover I do not like to apply it because it seems to me erroneous and to act in the wrong direction in as much as unmarried women can obtain employment more readily in the town and in the country and celibacy is therefore more likely to be common in the former and in the latter e. the possible difference of the length of an urban and rural generation must not be forgotten we however have reason to believe that the correction on this ground will be insignificant because the length of a generation is found to be constant under very different circumstances of race and therefore we should expect it to be equally constant in the same race under different conditions such as it is it would probably tell against the towns there is now some of the results not to be applied for D and E so we have only to regard A multiplied by B multiplied by C that this a calculation displayed on the page of open parenthesis 2,681 multiplied by 74 divided by 100 multiplied by 1,539 divided by 1,700 close parenthesis divided by open parenthesis 2,911 divided by 86 divided by 100 multiplied by 1,595 divided by 1,700 close parenthesis equals 1,796 divided by 2,334 equals 77 divided by 100 in other words the rate of supply in towns to the next adult generation is only 77% or say 3 quarters of that in the country this decay of the continued constant will lead to the result that the representatives of the townsmen will be less than half as numerous as those of the country folk after one century only about one fifth as numerous after two centuries their proportions being 45 divided by 100 and 21 divided by 100 respectively table 1 is displayed on the page census returns of 1,000 families of factory hands and coventry and 1,000 families of agricultural laborers in Warwickshire grouped according to the age of the mother and the number of children in the family 1, these 3 cases are anomalous the factory being less than the agricultural in the instance of 20 to 33 the anomalies double because the sequence of the figures shows that neither of these can be correct certainly not the first of them note, it will be observed to the left of the outline that is in the upper and left hand of the table where the mothers are young and the children few the factory families predominate while the agricultural are the most nearest between the outlines especially in the middle of the table where the mothers are less than young and the families are from 4 to 5 in number the two are equally numerous to the right of the outlines that is to the right of the table where the families are large table 2 is displayed on the following page with the number of families and number of children split between four different columns of factory and agricultural each and the four rows are within outline between outlines, beyond C an apparatus for testing the delicacy with which weights can be discriminated by handling them right at the end of the pathological institute November 14, 1882 I submit a simple apparatus that I have designed to measure the delicacy of the sensitivity of different persons as shown by their skill in discriminating weights, identical in size, form and colour, but different in specific gravity as interest lies in the accordance of the successive test values with the successive graduations of the true scale of sensitivity in the ease with which the tests are applied and the fact that the same principle can be made use of in testing the delicacy of smell and taste I use test weights that mount in a series of just perceptible differences to an imaginary person of extreme delicacy of perception, their values being calculated according to Weber's law the lowest weight is heavy enough to give a decided sense of weight to the hand when handling it and the heaviest weight can be handled without any sense of fatigue they therefore conform with close approximation to a geometric series thus and they bear as register marks the values of the successive indices 0, 1, 2, 3 etc it follows that if a person can just distinguish between any particular pair of weights, he can also just distinguish between any other pair of weights whose register marks differ by the same amount there can be by one interpretation of the phrase that the dullness of muscular sense in any person is twice as great as in that of another person A it is that B is only capable of perceiving one greater difference where A can perceive two, we may of course state the same fact inversely and say that the delicacy of muscular sense is in that case twice as great in A as in B similarly in all other cases of the kind, conversely if having known nothing previously about either A or B, we discover on trial that A can just distinguish between two weights such as those bearing the register marks 7 and that B can just distinguish between another pair say bearing the register marks 2 and 6 then since the difference between the marks in the latter case is twice as great as in the former we know that the dullness of the muscular sense of B is exactly twice that of A the relative dullness of we prefer to speak in inverse terms and say the relative sensitivity is determined quite independently of the particular pair of weights used in testing them we noted that the conversion of results obtained by the use of one series of test weights into what would have been given by another series is a piece of simple arithmetic, the fact ultimately obtained by an apparatus of this kind being the just distinguishable fraction of real weight in my own apparatus the unit of weight is 2% that is a register mark 1 means 2% body introduced weights in the earlier part of the scale that dull with half units, that is with differences of 1% in another apparatus the unit of weight might be 3% then 3 grades of mine will be equal to 2 of the other and mine will be converted to the scale by multiplying them 2 out of 3 thus the results obtained by a different apparatus are strictly comparable a sufficient number of test weights must be used or trials made to eliminate the influence of chance it might perhaps be thought that by using a series of only 5 weights and requiring them to be sorted into their proper order by the sense of touch alone the chance of accidental success would be too small to be worth consideration it might be said that there are 5 by 4 by 3 by 2 or 120 different ways in which 5 weights can be arranged and as only one is right it must be 120 to 1 against a lucky hit but this is many fold too high an estimate because the 119 possible mistakes are by no means equally probable when a person is tested an approximate value of his grade of sensitivity is rapidly found and the enquirer becomes narrowed to finding out whether he can surely pass a particular level this stage in the enquiry there is little fear of a gross mistake he is little likely to make a mistake of double the amount in question and is almost certain that he will not make a mistake of treble the amount in other words it would never be likely to pull one of the test weights more than one step out of its proper place if he had 3 weights to arrange in their consecutive order 1, 2, 3 there are 3 by 2 equal 6 ways of arranging them of these he will be liable to the errors of 1, 3, 2 and of 2, 1, 3 but he would highly be liable to such gross areas as 2, 3, 1 or 3, 2, 1 or 3, 1, 2 therefore are the 6 permutations in which 3 weights may be arranged 3 have to be dismissed from consideration leaving 3 cases only to be dealt with are which 2 are wrong or was right for the same reason there are only 4 reasonable chances of error in arranging 4 weights in these 6 and arranging 5 weights instead of the 119 that were originally supposed these are 1, 2, 3, 5, 4 1, 3, 2, 4, 5 1, 3, 2, 5, 4 2, 1, 3, 4, 5 2, 1, 3, 5, 4 2, 1, 4, 3, 5 but exception might be taken to 2 even of these namely those that appear in the 3rd column where is found to be in just position with 2 in the 1st case and 4 with 1 in the 2nd so greater difference between 2 adjacent weights would be almost sure to attract the notice of the person who is being tested and make him dissatisfied with the arrangement considering all this together with the convenience of carriage and manipulation I prefer to use trays each containing only 3 weights the trial is being made 3 or 4 times in succession each trial there are 3 possibilities and only 1 success therefore in 3 trials the probabilities again uniform successes are as 27 to 1 and in 4 trials at 81 to 1 values of the weights after preparatory trials I adopted 1000 grains as the value of W and 120 as that of I but I am now inclined to think that 110 would have been better made the weights by filling blank cartridges with shot, wool and wads so as to distribute the weight equally and I chose the cartridges with a wad turning the edges over it with the instrument well known to sportsmen I wrote the corresponding value of the index of R on the Wad which each of them is closed to serve as a registered number that's the cartridge whose weight was W wire 4 was marked 4 the values were so selected that there should be as few varieties as possible there are 30 weights in all but only 10 varieties whose registered numbers are respectively 0, 1, 2, 3 3.5, 4.5, 5, 6, 7, 9, 12 the reason of this limitation of varieties was to enable the weights to be interchanged whenever there became reason to suspect that the eye had begun to recognise the appearance of any one of them and that the judgement might be influenced by that recognition and see to be wholly guided by this sense of weight we are so accustomed to deal with concurrent impressions that it is exceedingly difficult even with the best intention of good faith to ignore the influence of any corroborative impression that may be present it is therefore right to take precautions against this possible cause of inaccuracy the most perfect way would be to drop the weights each in a little bag or sheath of light material so that the operati could not see the weights while the ratio between the weights would not be sensibly changed by the additional weight of the bags I keep little bags for this purpose inside the box that holds the weights arrangement of the weights the weights are placed in sets of 3s each sets in a separate shallow tray and the trays lie in two rows in a box each tray bears the register marks of each of the weights it contains it is also marked boldly with a Roman numeral showing the difference between the register marks of the adjacent weights this difference indicates the greater sensitivity that the weights in the tray are designed to test thus the tray containing the weights w-i-0, w-i-3, w-i-6 3 is marked as in figure 1 and that which contains w-i-2, w-i-7, w-i-12 is marked as in figure 2 the following is the arrangement of the trays in the box the triplets they contain suffice for ordinary purposes a table is displayed on the page with six columns listed as just perceptible ratio, greater sensitivity sequence of weights, just perceptible ratio greater sensitivity and sequence of weights again but it will be observed that sequence of can also be obtained and again that it is easy to select doubles of weights for course the tests are to a maximum difference of 12 which may be useful in cases of more bitterly diminished sensitivity manipulation a tray is taken out the three weights that it contains are shopped by the operator who then passes them on to the experimenter he then necessitates with his hands in an unconstrained position and lifts the weights in turn between his finger and thumb the finger pressing against the top the thumb against the bottom of the cartridge guided by the touch alone he arranges them in the tray in what he conceives to be their proper sequence he then returns the tray to the operator in its result the operator then reshuffles the weights and repeats the trial it is necessary to begin with course preparatory tests to accustom the operator to the character of the work the inner tube the operator may begin to record results and the testing may go for several minutes until the hand begins to tire the judgement to be confused and blunders to a rise practice does not seem to increase the delicacy of perception after the first few trials so much as might be expected D whistles for testing the upper limits of audible sound in different individuals the base of the inner tube of which the whistle is the foremost end of a plug the limits of being advanced or withdrawn by screwing it out or in thus the depth of the inner tube of the whistle can be of a rider pleasure the more nearly the plug is screwed home the less is the depth of the whistle and the more swirl does its note become until the point is reached at which although the air that proceeds from it vibrates as violently as before as shown by its effect on a sensitive flame the note ceases to be audible the number of vibrations per second in the notable whistle or other closed pipe depends on its depth the theory of acoustic shows that a length of each complete vibration is four times the depth of the closed pipe and since experience proves that all sound whatever maybe its pitch is propagated at the same rate which under ordinary conditions of temperature and barometric pressure may be taken at 1,120 feet or 13,440 inches per second it follows that the number of vibrations in the note of a whistle may be found by dividing 140 by 4 times the depth measured in inches of the inner tube of the whistle this rule however supposes the vibrations of the air in the tube to be strictly longitudinal and ceases to apply when the depth of the tube is less than about one and a half times its diameter when the tube is reduced to a shallow pan a note may still be reduced by it but that note has reference rather to the diameter of the whistle than to its depth being sometimes apparently unaltered to increase depth the necessity of preserving a favorable portion between the diameter and the depth of the whistle is a reason why these instruments having necessarily little depth required to be made with very small bores the depth of the inner tube of the whistle at any moment is shown by the graduations on the outside instrument the lower portion of the instrument has formally made for me by the late Mr. Tisley Optician, Robton Road is a cap that surrounds the body of the whistle and is self-fixed to the screw that forms the plug when a complete turn of the cap increases or diminishes the depth of the whistle I am not equal to the interval between two adjacent threads of the screw for mechanical convenience a screw is used whose pitch is 25 to the inch therefore one turn of the cap moves the plug one twenty-fifth of an inch or ten two hundred and fiftieths the edge of the cap is divided into ten parts each of which corresponds to the tenth of a complete time and therefore to one two hundred and fiftieth of an inch hence in reading of the graduations the tens are shown on the body of the whistle and the units are shown on the edge of the cap the scale of the instrument having for its unit the two hundred and fiftieth part of an inch it follows that the number of vibrations in the note of the whistle is to be found by dividing thirteen thousand four hundred and forty by two hundred and fifty divided by four or eighty four thousand by the graduations read off its scale a short table is a next giving the number of vibrations calculated by this formula for different depths bearing in mind that the earlier entries can not be relied upon unless the whistle has a very minute bore and consequently a very feeble note a table of four clumps is displayed on the page displaying the scaled readings and a corresponding number of vibrations per second the largest whistle suitable for experiments on the human ear have an inner tube of about 0.16 inches in diameter which is equal to 40 units of the scale consequently in these instruments the theory of closed pipes sees it to be trustworthy when the depth of the whistle is less than about 60 units in short we cannot be sure of surrounding with them a higher note than one of 14,000 vibrations to the second unless we use tubes of still small bore in some of my experiments I was driven to use very fine tubes indeed not wider than those little glass tubes that hold the smallest leads for modern's pencils but I have tried without much success to reduce the note there should be both shrill and powerful and correspond to a battery of small whistles by flattering a piece of brass tube and passing another shade of brass up it and thus forming a whistle the whole width of the sheet but of very small diameter from front to back it made a powerful note but not a very pure one we also constructed an annular whistle by mains of three cylinders one sliding within the other two and graduated as before when the limits of audibility are approached the sound becomes much fainter and when the limit is reached the sound usually gives place to a peculiar sensation which is not sound but more like dizziness and which some person experienced to a high degree young people hear shriller sounds than all people and I am told there is a proverb in Dosechia that no agricultural labour who is more than 40 years old can hear a batsqueak the power of hearing shrill notes has nothing to do with the sharpness of hearing anymore the wide range of the keyboard or piano has to do with the sound of the individual strings we all have our limits and our limit may be quickly found by these whistles in every case the facility of hearing shrill sounds depends in some degree on the position of the whistle 40 years highest when it is held exactly opposite the opening of the year any roughness of the lighting of the auditory canal appears to have been marked to fit in checking the transmission of rapid vibrations when they strike the ear obliquely I myself feel this in a marked degree I have long noted the fact in respect to the buzz a mosquito I do not hear the mosquito much as it flies about but when it passes close by my ear I hear a ping a sudden as a witch is very striking Mr. Dalby the orist who whom I gave one of these instruments tells me he uses it for diagnosis when the power of hearing high notes is wholly lost the loss is commonly owing to failure in the nerves but when very deaf people are still able to hear high notes they are surrounded with force the nerves are usually alright and the fault lies in the lighting of the auditory canal E. Questions on visualising in other allied faculties the questions that I circulated were as follows there was an earlier non-complete form which I need not reproduce here the object of these questions is to elicit the degree to which different persons possess the power of seeing images in their mind's eye and a reviving past sensations from inquiries I've already made it appears that remarkable variations exist both in the strength and in the quality of these faculties and it is highly probable that a statistical inquiry into them will throw light upon more than one physiological problem before addressing yourself to any of the questions on the opposite page think of some deaf net object suppose it is your breakfast table as you sat down to it this morning and consider carefully the picture that rises before your mind's eye 1. Illumination is the image dim or fairly clear is this brightness comparable to that of the actual scene 2. Definition are all the objects pretty well defined at the same time or is the place of sharpest definition at only one moment more contracted than it is in a real scene 3. Colouring are the colours of the china of the toast, bread crust, mustard, meat, parsley or whatever may have been the table quite distinct and natural 4. Extend the field of view call up the image of some panoramic view the walls of your room might suffice can you force yourself to see mentally a wider range of it than could be taken in by any single glance of the eyes can you mentally see more than three faces of a die or more than one hemisphere of a globe at the same incident of time 5.   Persons can you recall with distinctness the features of all near relations with any other persons can you at will cause your mental image of any or most of them to sit, stand or turn slowly round can you deliberately set the image of a well known person and chair and see it with an utter distinctness to enable you to sketch it literally supposing yourself able to draw 8. Scenery do you preserve the recollection of scenery with much precision of detail and do you find pleasure in dwelling on it can you easily form mental pictures from the descriptions of scenery that are so frequently met within novels and books of travel 9. Comparison with reality what damage do you perceive between a very vivid mental picture caught up in the dark in a real scene have you ever mistaken a mental image for a reality when in health and a wide awake 10. Numerals and Dates are these invariably associated in your mind with any peculiar mental imagery whether of written or printed figures diagrams or colours if so explain fully and say if you can account for the association 11. Specialities if you happen to have special aptitudes for mechanics, mathematics either geometry or three dimensions or pure analysis mental arithmetic or chess playing, blindfold please explain fully how far your processes depend on the use of visual images and how far otherwise 12. Call it before your imagination the object specified in the sixth following progress number 8 to F and consider carefully whether your mental representation of them generally is in each group very faint faint, fair, good or vivid and comparable to the actual sensation light in colour and evenly coloured sky emitting all landscape first brighter than a gloomy a thick surrounding haze first white then successively blue yellow, green and red sound, the beat of rain against the window pains, the crack of a whip the church bell, the hum of bees the whistle of a railway the clinking of teaspoons and saucers the slam of a door smells, tyre, roses an oil lamp blown out hay, fire it's a fur coat gas, tobacco tastes, salt, sugar, lemon juice, raisins chocolate, carnage jelly touch, velvet, silk soap, gum, sand, dough a crisp dead leaf a prick of a pin other sensations, heat, hunger cold, thirst, fatigue, fever, drowsiness a bad cold 13. Music have you any aptitude for mental recording music or for imagining it 14. At different ages do you collect what your powers of visualising etc. were in childhood have they varied much with your recollection general remarks supplementary information written here or on a separate piece of paper will be acceptable end of appendix part 2 end of section 12


Hey, folks, as we've seen in recent episodes of Code Club, using Git and GitHub is just a tremendously powerful tool. If you don't buy into the idea that we can use Git for version control and keeping track of different versions in the history of our project, well, we've certainly also seen that we can exploit the niceness of the folks at GitHub to put up a website and to let us use their servers to run a reproducible pipeline as we did in the last episode. So as nice as all these features are on GitHub, really what's most important about Git is the ability to keep track of version control. In today's episode, I'm going to talk to you about a tool within Git called Rebase that can be used to rewrite or repackage old commits to make it easier for you to navigate and see what changes are made over the course of your project. Over here on GitHub, I'm at github.com, riffamonus slash trout index, all those s's and slashes. Anyway, we are in our projects repository here on GitHub. And if we go ahead and click on the upper right corner of this box, we'll see a clock going counterclockwise. And at least on mine, I've got 35 indicating that there have been 35 commits over the history of this project. Again, if we kind of scroll all the way down through here, we'll see back on September 7th, the initial commit when this was just a dream. Anyway, but if we scroll back more recent in history, we now see that there have been three days since I put up the rendering or the workflow that generates the website with the drought visualization that we created as part of the series. I've noticed two things in here. Well, on October 18th, a week or so ago, I created the index page, the web page that we see when you go to riffamonus.com slash riffamonus.org slash drought index. So we created that page in two steps. We created a hello world, just to kind of prove to ourselves that this was working, that we could render something from GitHub onto a web page. And then we made it pretty using our markdown. Also, if we then go forward to the next time I was working on this, you'll see that there are quite a few commits that I made on October 25th, where I created the pipeline. I created run pipeline.yaml all the way through the process of deleting the index.html file, so we could then recreate everything by rerunning the snakemake file and then recommitting everything. Anyway, there's a whole bunch of steps in here that could be squashed down together into a single step that we might call create and run workflow. So what I'm going to do is exactly that in today's episode of Code Club. We'll come back and do the simple case of these two commits and squash them down into one. And then we'll do the more complicated and truly only complicated because there's more commits to squash all these down into a single commit. On GitHub, one of the nice things is that we can track the changes of the repository and look at see what happened at each stage of a commit. And so where we have these two angled icons, the greater than and less than sign, we can see what the commit looked like at that point in the history. We could then see index.html for hello world. All it said was hello world, right? But if we come back to our history and then we come to what the commit looked like after the next commit, we come down and we see index.html, which then is the full fleshed out HTML version of the file, right? So I don't know that I really need to keep track of where it said hello world, right? If we come back to our history, we can also click on the individual commits to see what changes were made at each step. So for this first commit, the hello world commit, we see that we added hello world. If we come to the next commit, we see that we've made a couple changes. So we added to the get ignore the line dot vs code. I must have been seeing some of the files from vs code that I didn't want to commit. So I ignored that. And then also in the snake file, I indicated that we need to build out the drought.png file here, as well as the index.html file. This is saying minus, because we removed the line without a comma and added a line with the comma, right? Then we also added a rule here. And then in our environment file, we added our markdown, right? We can see all the individual changes that happened along the way, in addition to creating the index.rmd file, as well as the index.html file. So this is a split view where we can kind of see the differences side by side. We can also see the unified view where we see all of the changes together in a single column, right? So for example, in the snake file, we can see that we removed this line and added this line as well as index.html to the rule targets section of that snake file, right? So again, this can get a little bit cumbersome as we start thinking about longer and longer series of commits, like we had up here where we were making the pipeline. So again, I could look at this first commit and I see that I added in my demo. And over the course of the whole series of commits on October 25th, we could come to here and we could then say, well, this is how things look different. But this isn't really showing me the full change of things over the history of that series of commits on that day. What I'd like to do to make it easier to navigate all these different commits is to squash them together to make it basically a single commit so I can look at the before and after of what the project looked like instead of looking at each different step of the commit history. To do all this, we'll come over to Visual Studio Code. And I don't know that I need to be in an environment, but it's always good to do it. And so I'll start out by doing conda, activate drought, and I'll do a get status. And if I do a get log. And so we see the last commit that I made was generate pretty index page. And so if I come back to my history, that was before I implemented the workflow. So I need to go ahead and do a get pull. So I'll do that get pull to pull down those additional changes that were created to bring about the workflow. Now if I do get status and get log, I now see that I've got new days rendering for yesterday afternoon, as well as the Wednesday, the Tuesday, as well as kind of that section of code that allowed me to build out that workflow. So to squash together different commits, we're going to use a function within Git called get rebase. So to use get rebase, I need to know what commit I want to go back to. So we've seen that with get log that we can see all these different commits, I could certainly also go back to GitHub. Another more convenient way is to say get log, and then to use the one line argument. And so this then puts each commit on a separate line, right.  I'm going to go ahead and grab this commit hash, right? And I'll copy that. And then I'll do get rebase hyphen, I so the hyphen I is for interactive. I've only ever seen get rebase use in interactive mode. So what I'm showing you, although there are many different arguments and options for using rebase, what I'm going to be showing you today is the most commonly used. So I'll go ahead and do get rebase hyphen, I and then I'm going to put in the hash code there. This then opens up for me here in nano, it's a bit odd that I'm using a text editor IDE like VS code, and I'm using nano, I suspect if I knew how to use the tool better, it would probably open up in the text editor for VS code, but whatever. So what we see here are the last 16 commits. And again, for now, I want to squash together these first two commits. And so what I will do is come down to the second one. And I want to squash this second one together with the first one. And so instead of pick, I'll put in squash, this will squash that 16th and 15th commits together. I'll go ahead and save this. And then exit out with control X. This then opens up a interactive way of defining a commit message that says this is the combination of two commits. This is the first commit message, Hello, world. This is commit message number two, generate pretty index page. And so I actually want to use the generate pretty index page as the name of my commit. So I'll go ahead and do control K to cut that and then control you to uncut that. And then I'll go ahead and delete these lines. And I'll again save with control O, and then control X. Now, if I do get log hyphen hyphen one line, I see that I now have squashed those two commits together to generate pretty index page. And I no longer have that Hello world. Now what I can do is I can then push this up to GitHub. And to do that, I can do get push. However, this causes a problem. And the problem is that we are rewriting history that we have already made public to the world. So one of the challenges of using git rebase is that you're rewriting history. And so, yes, we're rewriting history, we're not really deleting any commits, we're kind of repackaging them. But if you make this public and someone needed that Hello world commit, or they were depending on that Hello world commit existing, or they'd already pulled down a copy of my repo, they wouldn't have all the commits that I have, or actually, they'd have more commits that I have, right, there'd be that inconsistency. And so there's a trade off between rewriting history that you have perhaps made public and making your history a little bit more concise, right. So there is a bit of a trade off. Some people love git rebase, some people absolutely hate git rebase and think it's antithetical to the whole idea of version control. Anyway, I'm not going to take a site. I don't know that anyone pulled down my version of this repository, maybe you have, but what it's more important to me is showing you how we can use git rebase to make our repository a bit simpler. So now what we can do is git push hyphen hyphen force. So git push hyphen hyphen force will force the pushing of the updated repository up to GitHub. And now if I come back to my history, and I do a refresh, I now see that basically the whole commit history has been moved up to October 28, which is today, maybe I don't care so much about the day, but generate pretty index page is all squashed together as a single commit. Whereas before it was to separate commits. And again, if I look at the changes of what happened in this commit, I see that that VS code, I see the addition of the index dot HTML file. I see all these modifications to the snakemake file, the addition of our markdown to the environment file, and then the creation of index dot RMD, as well as the presence now of index dot HTML and all of that is new. There's no legacy of that Hello World index file. And now what I'd like to do is to do another iteration of git rebase to go ahead and squash together all of the commits that went into making the workflow and running the workflow. So let's come back and again, we'll do git log hyphen hyphen one line. And the commit I want to go back to, of course, is that generate the pretty index page. So we'll come back to here. I'll copy that. And then I'll do git rebase hyphen, I, and then the first seven or so characters of that hash code. Again, this brings up our interactive git rebase interface. And I again am going to leave the first one as pick. That means we want this commit, and then everything else below it, I'm going to squash into that. So I'll go ahead and remove this pick and do squash, as well as this. Again, if you have a fancy text editor, that might make a lot of this editing a lot easier. But nanos, okay, and squash. Right. And so then new days rendering, I'm going to go ahead and squash that into as well as specify time. That was when we changed it from going on a push to on a schedule. And then I'll also do this one, where we deleted the PNG and HTML file to make sure that when we updated the workflow that there was actually something that had changed to then commit. And I will then leave those new days renderings for the last three days in here. So now again, I can go ahead and do a control Oh, and control X to save and exit. Again, this brings me to my commit message. I'm going to go ahead and use control K to delete out all of these lines in here. And I will write a new commit message. So I'll say create get hub actions workflow to run snake make pipeline. And I'll save that. And then I'll exit out. And so now here's the test. I do get log hyphen hyphen one line. I now see that I've got create GitHub actions workflow to run snake make pipeline, generate pretty index page. This we saw was maybe a dozen different commits that were kind of tweaking one thing at a time as we're building out that YAML file that ran the workflow or that changed the snake make to add in the conda environments and things like that. Right. And so on the whole, all those changes now are condensed down into a single commit, which makes it a lot easier to go back and see what has changed at each stage. So again, I'll go ahead and hit Q to get out of that view. Again, if I then do get push hyphen hyphen force, again, because we did rewrite the history, some history that we'd already made public. So we need that hyphen hyphen force to force pushing it up to GitHub, coming back to my commit history here on GitHub. I'll go ahead and refresh the page. And so now what I see is I still have these three new day renderings, but again, create GitHub actions workflow to run snake make pipeline is the commit after generate pretty index page. And if I click on this commit, so again, I see the creation of the run pipeline dot YAML file. For my purposes, I don't need to see the iteration and development of this file. I suppose if you had a version that was working, and you liked it, and then you came back the next day and made some changes to update it, I probably wouldn't squash those two commits together. Because maybe you change something in between that breaks the workflow. And so then you wouldn't really be able to go back to before the change, right? And so you have to be thoughtful about what you're squashing together, because you can't really go back very easily into a commit that you had already squashed together, right? So you have to be confident that the things belong together in a single commit, and that things didn't break after that subsequent commit. So then we have these changes to the snake file again, where we added things. And I think this all looks pretty good. Again, adding the environment file, and then the change to the index page. So obviously, I also deleted the index dot HTML, and world drought dot PNG file, that'd probably be good to leave those in there. And you know what, maybe I will come back and add those in. So again, I could do another get rebase on that. And I think I'll squash the first new days rendering in with the pick. And I will then save and commit that out. And I will go ahead and use the create GitHub actions workflow as the commit message. So again, I'll save that, get push hyphen hyphen force and then refresh. And so now we see that we have that create GitHub actions workflow. And again, if we scroll down to the end, we see that we did have the deleted and added versions of the workflow, the one from the 17th to the one from the 25th. Again, I think that's enough said about GitHub rebase. Again, know that there is a bit of controversy in whether or not we should be rewriting or reworking the history. Once it's been made public, the downsides of using get rebase is that someone else has perhaps taken a copy of your repository, your histories might not align with each other. The other downside of get rebase is that say you make a commit, but you hadn't fully tested your code, if you squash that new commit together with the old commit, then it won't be possible, at least not very easily to go back before the last commit that you made to figure out what changed to break your results. Again, if you're confident though that things work after you make those subsequent commits, go ahead and squash them together. And you can think of that commit as representing a single feature that you have added to your repository. And that's exactly what we did. We added the single feature of running a snake make workflow with GitHub actions up on GitHub. So this is obviously a little bit more of an advanced concept and using get and version control. But I think it also is useful for helping us to think about how we can organize our version history of our repository. And that's really valuable because ultimately, get is about version control and being able to look back through the history and to see how things have changed, right? So if our version history is like just a big dumpster file, then that's not very helpful. I know people find this very useful when they're making subtle tweaks trying to get something to work. And they make a commit after each change. And so they have a version history that says trying this trying something else, or they start inserting f bombs or all sorts of other crazy things. And so get rebase will help them to squash all those together into a single commit. And I think that is a very useful application for using get rebase. All right, give this a shot with some of your projects. Let me know how it goes. And we'll see you next time for another episode of Code Club.