Section 18 of Micrographia. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Micrographia by Robert Hooke. Observation 13. Of the small diamonds or sparks in flints. Chancing to break a flint stone in pieces, I found within it a certain cavity or crusted over with a very pretty candied substance, some of the parts of which, upon changing the posture of the stone in respect of the incident light, exhibited a number of small but very vivid reflections.  Having considered those vivid repercussions of light, I found them to be made partly from the plain external surface of these regularly-figured bodies, which afforded the vivid reflections, and partly to be made from within the somewhat-pollucid body, that is, from some surface of the body opposite to that superfices of it, which was next the eye. And because these bodies were so small that I could not welcome to make experiments and examinations of them, I provided me several small sterii of crystals or diamants, found in great quantities in Cornwall, and are therefore commonly called Cornish Diamants. These being very pollucid and growing in a hollow cavity of a rock, as I have been several times informed by those that have observed them, much after the same manner as these do in the flint, and having besides their outward surface very regularly shaped, retaining very near the same figures with some of those I observed in the other, became a convenient help to me for the examination of the proprieties of those kinds of bodies. And first for the reflections, in these I found it very observable, that the brightest reflections of light proceeded from within the pollucid body, that is, that the rays admitted through the pollucid substance in their getting out on the opposite side, were by the contiguous and strong reflecting surface of the air very vividly reflected, so that more rays were reflected to the eye by this surface, though the ray in entering and getting out of the crystal had suffered a double refraction, than there were from the outward surface of the glass, where the ray had suffered no reflection at all. And that this was the surface of the air that gave so vivid a repercussion, I tried by this means, I sunk half of a sterii in water, so that only water was contiguous to the under surface, and then the internal reflection was so exceedingly faint, that it was scarce discernable. Again I tried to alter this vivid reflection by keeping off the air, with a body not fluid, and that was by rubbing and holding my finger very hard against the under surface, so as in many places the pulp of my finger did touch the glass without any interjacent air between. Then observing the reflection, I found that where so ever my finger or skin touched the surface, from that part there was no reflection, but in the little furrows or creases of my skin, where there remained little small lines of air, from them was returned a very vivid reflection as before. I tried further by making the surface a very pure Quicksilver to be contiguous to the under surface of this pollucid body, and then the reflection from that was so exceedingly more vivid than from the air, as the reflection from air was then the reflection from the water. From all which trials I plainly saw that the strong reflecting air was the cause of this phenomenon. And this agrees very well with the hypothesis of light and pollucid bodies, which I have mentioned in the description of Muscovy Glass, for we there suppose glass to be a medium, which does less resist the pulse of light, and consequently that most of the rays incident on it enter into it, and are refracted towards the perpendicular, whereas the air I suppose to be a body that does more resist it, and consequently more are repercussed than do enter it. The same kind of trials have I made with crystalline glass, with drops of fluid bodies, and several other ways which do all seem to agree very exactly with this theory, so that from this principle, well established, we may deduce several corollaries not unworthy observation. And the first is that it plainly appears by this, that the production of the rainbow is as much to be ascribed to the reflection of the concave surface of the air as to the refraction of the globular drops. This will be evidently manifest by these experiments. If you foliate that part of a glass ball, that is to reflect an iris, as in the Cartesian experiment above mentioned, the reflections will be abundantly more strong, and the colours more vivid, and if that part of the surface be touched with water, scarce affords any sensible colour at all. Next we learn that the great reason why pollucid bodies, beaten small, are white, is from the multitude of reflections, not from the particles of the body, but from the contiguous surface of the air. And this is evidently manifested by filling the interstitiality of those powdered bodies with water, whereby their whiteness presently disappears. From the same reason proceeds the whiteness of many kinds of sands, which in the microscope appear to be made up of a multitude of little pollucid bodies, whose brightest reflections may, by the microscope, be plainly perceived to come from their internal surfaces, and much of the whiteness of it may be destroyed by the effusion of fair water to be contiguous to those surfaces. The whiteness also of froth is for the most part to be ascribed to the reflection of the light from the surface of the air within the bubbles, and very little to the reflection from the surface of the water itself. For this last reflection does not return a quarter so many rays as that which is made from the surface of the air, as I have certainly found by a multitude of observations and experiments. The whiteness of linen, paper, silk, etc. proceeds much from the same reason as the microscope will easily discover, for the paper is made up of an abundance of pollucid bodies which afford a very plentiful reflection from within, that is, from the concave surface of the air contiguous to its component particles. Wherefore, by the effusion of water, oil, tallow, turpentine, etc., all those reflections are made more faint, and the beams of light are suffered to reject and run through the paper more freely. Hence further we may learn the reason of the whiteness of many bodies, and by what means they may be in part made pollucid. As white marble, for instance, for this body is composed of a pollucid body exceedingly flawed. That is, there are abundance of thin and very fine cracks or chinks amongst the multitude of particles of the body that contain in them small parcels of air, which do so repercuss and drive back the penetrating beams that they cannot enter very deep within that body, which the microscope does plainly inform us to be made up of a congeries of pollucid particles. And I further found it somewhat more evidently by some attempts I made towards the making transparent marble, for by heating the stone a little and baking it in oil, turpentine, oil of turpentine, etc., I found that I was able to see much deeper into the body of marble than before, and one trial, which was not with an unctuous substance, succeeded better than the rest, of which, when I have a better opportunity, I shall make further trial. This also gives us a probable reason of the so much admired phenomena of the Oculus Mundi, an oval stone which commonly looks like white alabaster, but being laid a certain time in water it grows pollucid and transparent, and being suffered to lie again dry, it by degrees loses that transparency and becomes white as before. For the stone being of a hollow spongy nature, has in the first and last of these appearances all those pores filled with the octunding and reflecting air, whereas in the second all those pores are filled with a medium that has much the same refraction with the particles of the stone, and therefore those two being contiguous make, as twer, one continued medium, of which more is said in the fifteenth observation. There are a multitude of other phenomena that are produced from this same principle, which, as it has not been taken notice of by any yet that I know, so I think, upon more diligent observation, will it not be found the least considerable. But I have here only time to hint hypothesis, and not to prosecute them so fully as I could wish. Many of them having a vast extent in the production of a multitude of phenomena which have been by others either not attempted to be explained or else attributed to some other cause than what I have assigned, and perhaps than the right. And therefore I shall leave this to the prosecution of such as have more leisure. Only before I leave it I must not preterm it to hint that by this principle multitudes of the phenomena of the air, as about mists, clouds, meteors, halos, etc., are most plainly and perhaps truly explicable. Multitudes also of the phenomena in coloured bodies, as liquours, etc., are deducible from it. And from this I shall proceed to a second considerable phenomenon which these diamants exhibit, and that is the regularity of their figure, which is a propriety not less general than the former, it comprising within its extent all kinds of metals, all kinds of minerals, most precious stones, all kinds of salts, multitudes of earths, and almost all kinds of fluid bodies. And this is another propriety which, though a little superficially taken notice of by some, has not, that I know, been so much as attempted to be explicated by any. This propriety of bodies, as I think it the most worthy, and next in order to be considered after the contemplation of the globular figure, so have I long had a desire as well as a determination to have prosecuted it if I had had an opportunity, having long since proposed to myself the method of my inquiry therein, it containing all the allurements that I think any inquiry is capable of. For first I take it to proceed from the most simple principle that any kind of form can come from. Next the globular, which was therefore the first I set upon and what I have therein performed I leave the judicious reader to determine. For as that form proceeded from a propriety of fluid bodies which I have called congruity, or incongruity, so I think, had I time and opportunity, I could make probable that all these regular figures that are so conspicuously various and curious and do so adorn and beautify such multitudes of bodies as I have above hinted, arise only from three or four several positions or postures of globular particles and those the most plain, obvious and necessary conjunctions of such figured particles that are possible. So that supposing such and such plain and obvious causes concurring the coagulating particles must necessarily compose a body of such a determinant, regular figure, and no other. And this with as much necessity and obviousness as a fluid body encompassed with a heterogeneous fluid must be protruded into a spherule or globe. And this I have, ad oculum demonstrated with a company of bullets and some few other very simple bodies so that there was not any regular figure which I have hitherto met with all of any of those bodies that I have above named that I could not with the composition of bullets or globules and one or two other bodies imitate even almost by shaking them together. And thus for instance we may find that the globular bullets will of themselves if put on an inclining plane so that they may run together naturally run into a triangular order composing all the variety of figures that can be imagined to be made out of equilateral triangles and such will you find upon trial all the surfaces of alum to be composed of for three bullets lying on a plane as close to one another as they can compose an equilateral triangular form as in A in the seventh scheme if a fourth be joined to them on either side as closely as it can they for compose the most regular rhombus consisting of two equilateral triangles as B if a fifth be joined to them on either side in as closer position as it can which is the propriety of the texture it makes a trapezium or four sided figure two of whole angles are 120 and two 60 degrees as C if a sixth be added as before either it makes an equilateral triangle as D or a rhomboid as E or an hexangular figure as F which is composed of two primary rhombs if a seventh be added it makes either an equilateral hexagonal figure as G or some kind of six sided figure as H or I and though there be never so many placed together they may be ranged into some of these lately mentioned figures all the angles of which will be either 60 degrees or 120 as the figure K which is an equiangular hexagonal figure is compounded of 12 globules or maybe of 25 or 27 or 36 or 42 etc and by these kinds of texture or position of globular bodies may you find out all the variety of regular shapes into which the smooth surfaces of alum are formed as upon examination anyone may easily find nor does it hold only in superfices but in solidity also for it's obvious that a fourth globule laid upon the third in this texture poses a regular tetrahedron which is a very usual figure of the crystals of alum and to hasten there is no one figure into which alum is observed to be crystallized but may by this texture of globules be imitated and by no other I could instance also in the figure of sea salt a sal gem that it is composed of a texture of globules placed in a cubicle form as al and that all the figures of those salts may be imitated by this texture of globules and by no other whatsoever and that the forms of vitriol and of saltpeter as also of crystal, horfrost etc are compounded of these two textures but modulated by certain proprieties but I have not here time to insist upon as I have not neither to shoe by what means globules come to be thus context and what those globules are and many other particulars requisite to a full and intelligible explication of this propriety of bodies nor have I hitherto found indeed an opportunity of prosecuting the enquiry so far as I designed nor do I know when I may it requiring abundance of time and a great deal of assistance to go through with what I designed the model of which was this first to get as exact and full a collection as I could of all the differing kinds of geometrical figured bodies some three or four bodies of each kind secondly with them to get as exact a history as possibly I could learn of their places of generation or finding and to inquire after as many circumstances that tended to the illustrating of this enquiry as possibly I could observe thirdly to make as many trials as upon experience I could find requisite in dissolutions and coagulations of several crystallizing salts for the needful instruction and information in this enquiry fourthly to make several trials on diverse other bodies as metals, minerals and stones by dissolving them in several menstruums and crystallizing them to see what figures would arise from those several compositums fifthly to make compositions and coagulations of several salts together into the same mass to observe of what figure the product of them would be and in all to note as many circumstances as I should judge conducive to my enquiry sixthly to inquire the closeness or rarity of the texture of these bodies by examining their gravity and their refraction etc seventhly to inquire particularly what operations the fire has upon several kinds of salts what changes it causes in their figures textures or energies eighthly to examine their manner of dissolution or acting upon those bodies dissoluble in them the texture of those bodies before and after the process and this for the history next for the solution to have examined by what and how many means such and such figures actions and effects could be produced possibly and lastly from all circumstances well weighed I should have endeavored to have shown which of them was most likely and if the informations by these enquiries would have borne it to have demonstrated which of them it must be and was but to proceed as I believe it next to the globular the most simple so do I in the second place judge it not less pleasant for that which makes an enquiry pleasant are first a noble inventum that promises to crown the successful endeavor and such must certainly the knowledge of the efficient and concurrent causes of all these curious geometrical figures be which has made the philosophers hitherto to conclude nature in these things to play the geometrician according to that saying of Plato or next a great variety of matter in the enquiry and here we meet with nothing less than the mathematics of nature having every day a new figure to contemplate or a variation of the same in another body which do afford us a third thing which will yet more sweeten the enquiry and that is a multitude of information we are not so much to grope in the dark as in most other enquiries where the inventum is great for having such a multitude of instances to compare and such easy ways of generating or compounding and of destroying the form as in the solution and crystallization of salts we cannot but learn plentiful information to proceed by and this will further repair from the universality of the principle which nature has made use of almost in all inanimate bodies and therefore as the contemplation of them all conduces to the knowledge of any one so from a scientific knowledge of any one does follow the same of all and everyone and fourthly for the usefulness of this knowledge when acquired certainly none can doubt that considers that it carries us a step forward into the labyrinth of nature in the right way towards the end we propose ourselves in all philosophical enquiries so that knowing what is the form of inanimate or mineral bodies we shall be the better able to proceed in our next enquiry after the forms of vegetative bodies and last of all of animate ones that seeming to be the higher step of natural knowledge that the mind of man is capable of end of section 18 section 19 of Micrographia this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Micrographia by Robert Hook section 19 observation 14 of several kinds of frozen figures I have very often in the morning when there has been a great half frost with an indifferently magnifying microscope observed the small styria or crystalline beard which then usually covers the face of most bodies that lie open to the cold air and form them to be generally hexangular prismatic bodies much like the long crystals of saltpeter save only that the ends of them were differing for whereas those of Nitra are for the most part pyramidal being terminated either in a point or edge these are froze through a hollow and the cavity in some seem pretty deep and this cavity was the more plainly to be seen because usually one of the other of the thicks that the medium size was wanting or at least much shorter than the rest but this was only the figure of the bearded half frost and as for the particles of other kinds of half frost they seem for the most part irregular of no certain figure nay, the parts of those curious branching or vortices that usually in cold weather tarnished the surface of glass appear through the microscope very rude and unshapen as do most other kinds of frozen figures which to the naked eye seem exceedingly neat and curious the figures of snow, frozen urine, hail several figures frozen in common water, etc some observations of each of which I shall hear unto a next because if well considered and examined they may perhaps prove very instructive for finding out of what I have endeavoured in the preceding observation to shoo to be next to globular figure which I caused by congruity as I hope I have made probable in the sixth observation the most simple and plain operation of nature of which nonewithstanding we are yet ignorant first, several observables in the sixth branch figures formed on the surface of urine by freezing one, the figures were all frozen almost even with the surface of the urine and the vessel but the bigger stems were a little prominent above the surface and the parts of those stems which were nearest the center a, were biggest above the surface two, I have observed several kinds of these figures some smaller, no bigger than the two pans others so big that I have by measure found one of its stems or branches above four foot long and of these some were pretty round having all their branches pretty near alike, others of them were more extended towards one side as usually those very large ones were which I have observed in ditches which have been full of full water three, none of all these figures I have yet taken notice of had any regular position in respect of one another or of the sides of the vessel nor did I find any of them equally to exactness extended every way from the center a four, wherever there was a center the branching from it a b, a c, a d, a e, a f, a g were never fewer or more than six but usually concured or met another very near the same point or center a though often times not exactly and were inclined to each other by an ankle a very near 60 degree I say very near because though having endeavour to measure them to most accurately I was able with the lyre just compasses I had I could not find any sensible variation from that measure yet the whole six branched figures seem to compose a solid angle they must necessarily be somewhat less five the middle lines or stems of these branches a b, a c, a d, a e, a f, a g seemed somewhat wider and a little higher than any of those intermediate branchings of these figures and the center a was the most prominent part of the whole figure seeming a pex of a solid angle or pyramid each of the six planes being a little inclined below the surface of the urine six the lateral branches ishing out of great ones such as op, mq, etc. were each of them inclined to the great ones by the same angle of about 60 degrees as the great ones were to another and always the bigger branchings were prominent above the less and the less above the least by proportionate gradations seven the lateral branchings shooting out of the great ones went all of them from the center and each of them was parallel to that great branch next to which it lay so that as all the branches on one side were parallel to one another so were they all of them to the approximate great branch as po, qr as they were parallel to each other and shot from the center so they were parallel also to the great branch ab eight some of the stems of the six branches proceeded straight and of the thickness that gradually grew sharper towards the end as ag nine other of the stems of those branches grew bigger and nutty towards the middle and the branches also as well as stems from cylinders grew into plates in a most admirable and curious order so exceedingly regular and delicate that nothing could be more as is visible in ab, ac, ad, ae, af but towards the end of some of these stems they began again to grow smaller and to recover their former branchings as about k and n ten many of the lateral branches had co-lateral branches if I may so call them sqm had many such as st and most of those again sub-co-lateral as vw and these again had others less which one may call lateral sub-co-lateral and these again others and they others etc in greater figures eleven the branchings of the main stems joined not together by any regular line not that one side of the one lay over the other side of the other but the small co-lateral and sub-co-lateral branches did lie atop of one another according to a certain order or method which I always observed to be this twelve the side of a co-lateral or sub-co-lateral etc branch lay over the side of the approximate as feathers in the wings of a bird whose branchings proceed parallel to the biggest stem from which it sprung and not to the biggest stem of all unless that were second stem backwards thirteen this wool that held in the branchings of the sexangular figure held also in the branchings of any other great or small stem though it did not proceed from a center fourteen the exactness and curiosity of the figuration of these branches was in every particular sub-transcendent that I judge it almost impossible for humane art to imitate fifteen tasting several clear pieces of this ice I could not find any urinous taste in them but those few I tasted seemed as insipid as water sixteen a figuration somewhat like this though indeed in some particulars much more curious I have several times observed in regular martyrs' stilatos but with this difference that all the stems and branchings are bended in a most excellent and regular order whereas in ice the stems and branchings are straight but in all other particulars it agrees with this and seems indeed nothing but of these stars or branched figures frozen on urine distorted or west a little with certain proportions lead also has arsenic and some other things mixed with it I have found to have this surface when suffered to cool figured somewhat like the branchings of urine but much smaller seventeen but there is a vegetable which does exceedingly imitate these branches and that is fern where the main stem may be observed branches and the stem of each of these lateral branches then fourth collateral branches and subcollateral branches and those lateral subcollateral etc and all those much after the same order with branchings, divisions and subdivisions and their branchings of these figures and frozen urine so that if the figures of both be well considered one would guess that there were not much greater need of a seminal principle for the production of fern then for the production of the branches of urine or the stellar martis there seem to be much form and beauty in one of the other and indeed this plant of fern if all particulars be well considered will seem as simple and uncompowded a form as any vegetable next to mulch or mushrooms and would next after the invention of the forms of those deserved to be inquired into for nonwithstanding several have affirmed to have seed and to be propagated thereby yet though I have made very diligent inquiry after that particular I cannot find that there is any part of it that can be imagined to be more seminal than another but this on here by the by for the freezing figures in urine I found it requisite first that the superficies be not disturbed with any wind or other accommodation of the air or the like secondly that it be not too long exposed so as that the whole bulk be frozen for often times in such cases by reason of the swelling of the eyes or from other cause the curious branch figures disappear thirdly an artificial freezing with snow and salt applied to the outside of the containing vessel succeeds not well unless there be very little quantity in the vessel fourthly if you take any clear and smooth glass and wetting all the inside of it with urine you expose it to a very sharp freezing you will find it covered with a very regular and curious figure two observables in figured snow exposing a piece of black cloth or black hat to the falling snow I have often with great pleasure observed such an infinite variety of curiously figured snow that it would be impossible to draw the figure and shape of every one of them as to imitate exactly the curious and geometrical mechanism of nature in any one some caused warts such as the coldness of the weather and the ill provisions I had by me for such a purpose would permit me to make I have here added in the second figure of the 8th scheme in all which I observed that if they were any regular figures they were always branched out with 6 principle branches all of equal lengths, shape and make from the center being each of them inclined either of the next branches on either side of it by an angle of 60 degree no as all the stems were for the most part in one flake exactly of the same make so were they in different figures of very different ones so that in a very little time I have observed above 100 several sizes and shapes of these dairy flakes the branches also out of each stem of any one of these flakes were exactly alike in the same flake so that of whatever figure one of the branches were the other 5 were surely to be of the same very exactly that is if the branchings of the one were small parallely pipettes or plates the branchings of the other 5 were of the same and generally the branchings were very conformable to the rules and method observed before and the figures on urine that is the branching from each side of the stems were parallel to the next stem on that side and if the stems were plated the branches also were the same if the stems were very long the branches also were so etc Observing some of these figured flakes with a microscope I found them not to appear so curious and exactly figured as one would have imagined but like artificial figures the bigger they were magnified the more irregularities appeared in them but this irregularity seemed ascribable to the thawing and breaking of the flake by the fall and not at all to the defect of the plastic virtue of nature whose curiosity in the formation of most of these kind of regular figures such as those of salt, minerals etc appears by the help of the microscope to be very many degrees smaller than the most acute eye as able to perceive with audit and though one of these six branched stars appeared here below much of the shape described in third figure of the 8th scheme yet I'm very apt to think that could we have a side of one of them through a microscope as they are generated in the clouds before their figures are vitiated by external accidents they would exhibit abundance of curiosity and neatness there also though never so much magnified for since I have observed the figures of salts and minerals to be some of them so exceedingly small that I have scarcely been able to perceive them with the microscope and yet they have been regular and since as far as I have yet examined it there seems to be but one and the same cause that produces both these effects I think it not irrational to suppose that these pretty figure stars of snow when it first generated might also be very regular and exact third several kinds of figures and water frozen putting fair water into a large capacious vessel of glass and exposing it to the cold observed after a little time several broad flat and thin laminé or plates of ice crossing the bulk of the water and one another very irregularly only most of them seemed to turn one of their edges toward that side of the glass which was next to it and seemed to grow as to where from the inside of the vessel inwards towards the middle almost like so many plates of fern having taken several of these plates out of water on the plate of a knife I observed them figured much after the manner of herring bones of fern blades that is there was one bigger stem in the middle like the backbone and out of it on either side there were a multitude of small starier or icicles like the smaller bones or the smaller branches in fern each of these branches on the one side were parallel to all the rest on the same side and all of them seemed to make an angle with the stem towards the top of 60 degrees and towards the bottom or root of the stem of 120 the fourth figure on the eighth plate I observed likewise several very pretty varieties of figures in water frozen on the top of a broad flat marble stone exposed to the cold with a little water on it some like feathers some of other shapes many of them were very much of this shape expressed in the fifth figure of the eighth scheme which is extremely differing from any of the other figures I observed likewise that the shootings of ice on the top of the water beginning to freeze were in straight prismatic bodies much like those of rockpetar that they crossed each other usually without any kind of order or rule that they were always a little higher than the surface of the water that lay between them that by degrees those interiescent spaces would be filled with ice also which usually would be as high as the surface of the rest in flakes of ice that had been frozen on top of the water to any considerable thickness I observed that both the upper and the underside of it were curious to quilt, furrowed or grained as it were which when the sun shone on the plate was exceedingly easy to be perceived to be much after the shape of the lines the sixth figure on the eighth scheme that is they consisted of several straight ends of plates which were of diverse lengths and angles to one another without any certain order the cause of all which regular figures and hundreds of others namely of salts, minerals metals etc which I could have here inserted but did not have been too long seemed to be deducible from the same principles which I have in the 13th observation hinted only having not yet had time to complete a theory of them but indeed which I there also hinted I judged the second step by which the pyramid of natural knowledge which is the knowledge of the form of bodies is to be ascended and who so ever would climb it must be well furnished with that which the noble Vero Larum calls Scalam Intellectus he must have scaling ladders otherwise the steps are so large and high there will be no getting up them and consequently little hopes of attaining any higher station such as to the knowledge are the most simple principles of vegetation manifested in Mulder mushrooms which as I elsewhere endeavour to shoe seems to be the third step for it seems to me that the intellect of man is like his body destitute for wings and cannot move from a lower to a higher and more sublime station of knowledge otherwise then step by step nay even there where the way is prepared and already made passable as in the elements of geometry or the like where it is faint to climb a whole series of proposition by degrees before it attains the knowledge of one problem but if the ascent be high difficult and above it's reach must have recourse to another Morganum some new engine on country vents some new kind of algebra or analytic art before it can surmount it end of section 19 section 20 of micrographia this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org micrographia by Robert Hook section 20 observation 15 of Kettering stone and of the pores of inanimate bodies this stone which is brought from Kettering north Hamptonshire and digged out of a quarry as I am informed has a grain altogether admirable nor have I ever seen or heard of any other stone that has the like it is made up of an innumerable company of small bodies not all of the same size or shape but for the most part not much differing from a globular form nor exceed they one another in diameter above three or four times they appear to the eye like the cob or ovary of a herring or some smaller fishes for the most part the particles seem somewhat less and not so uniform but their variation from a perfect globular ball seems to be only by the pressure of the contiguous balls which have a little depressed and protruded those touched sides inward and forced the other sides as much outwards beyond the limits of a globe just as it would happen if a heap of exactly round balls of soft clay were heaped upon another or as I have often seen a heap of small globules of quick silver reduced to that form by rubbing it much in a glazed vessel with some slimy or sluggish liquor such a spittle when though the top of the upper globules be very near spherical yet those that are pressed upon by others exactly imitate the forms of these lately mentioned grains where these grains touch each other they are so firmly united or settled together that they seldom part without breaking a hole in one or the other of them such as A, A, A B, C, C etc. some of which fractions as A, A, A, A where the touch has been but light break no more than the outward crust or first shell of the stone which is of a white color a little dashed with a brownish yellow and is very thin like the shell of an egg and I have seen some of those grains perfectly resemble some kind of eggs both in color and shape but where the union of the contiguous granules has been more firm there the divulging has made a greater chasm as at B, B, B in so much that I have observed some of them quite broken in two as at C, C, C which has discovered to me a further resemblance they have to eggs they having an appearance of a white and yelk by two differing substances that envelop and encompass each other that which we may call the white was pretty whitish near the yelk but more dusky towards the shell of them I could plainly perceive to be shot or radiated like a pyrite or firestone the yelk in some I saw hollow in others filled with a dusky brown and porous substance like a kind of pith the small pores or interstitia E, E, E, E betwixt the globules I plainly saw and found by other trials to be every way pervious to air and water for I could blow through a piece of this stone of a considerable thickness as easily as I have blown through a cane which minded me of the pores which Descartes allowed his materia subtilis between the ethereal globules the object through the microscope appears like a congeries or heap of pibles such as I have often seen cast up on the shore by the working sea after a great storm or like in shape, though not color a company of small globules of quicksilver looked on with a microscope when reduced into that form by the way lately mentioned and perhaps this last may give some hint at the manner of the formation of the former for supposing some lapidescent substance to be generated or some way brought either by some comixter of bodies in the sea itself or protruded in perhaps out of some subterraneous caverns to the bottom of the sea and there remaining in the form of a liquor like quicksilver heterogenous to the ambience saline fluid it may by the working and tumblings of the sea to and fro be jumbled and communuted into such globules as may afterwards be hardened into flints the lying of which one upon the other when in the sea being not very hard by reason of the weight of the encompassing fluid may cause the undermost to be a little though not much varied by a globular figure but this only by the by after what manner this catering stone should be generated I cannot learn having never been there to view and observe the circumstances but it seems to me from the structure of it to be generated from some substance once more fluid and afterwards by degrees growing harder almost after the same manner as I supposed the generation of flints to be made but whatever were the cause of its curious texture we may learn this information from it that even in those things which we account vile rude and coarse nature has not been wanting to show abundance of curiosity and excellent mechanism we may here find a stone by help of a microscope to be made up of abundance of small balls which do but just touch each other and yet there being so many contacts they make a firm hard mass stone much harder than free stone next though we can buy a microscope discern so curious a shape in the particles yet to the naked eye there scarce appears any such thing which may afford us a good argument to think that even in these bodies also whose texture we are not able to discern though helped with microscopes there may be yet latent so curious a schematism that it may abundantly satisfy the curious searcher who shall be so happy as to find some way to discover it next we here find a stone though to the naked eye a very close one yet every way perforated with innumerable pores which are nothing else but the interstitia between those multitudes of minute globular particles that compose the bulk itself and these pores are not only discovered by the microscope but by this contrivance I took a pretty large piece of this stone and covering it all over with cement save only at two opposite parts I found myself able by blowing in at one end that was left open to blow my spittle with which I had wet the other end into an abundance of bubbles which argued these pores to be open and pervious through the whole stone which affords us a very pretty instance of the porousness of some seemingly close bodies of which kind I shall anon have occasion to subjoin many more tending to prove the same thing I must not here omit to take notice that in this body there is not a vegetative faculty that should so contrive this structure for any peculiar use of vegetational growth whereas in the other instances of vegetable porous bodies there is an anima or forma informans that does contrive all the structures and mechanisms of the constituting body to make them subservient and useful to the great work or function they are to perform and so I guess the pores in wood and other vegetables in bones and other animal substances to be as so many channels provided by the great and all wise creator for the conveyance of appropriated juices to particular parts and therefore that this may tend or be pervious all towards one part and may have impediments as valves or the like to any other in this body we have very little reason to suspect there should be any such design for it is equally pervious every way not only forward but backwards and sideways and seems indeed much rather to be a homogenous or similar to those pores which may with great probability believe to be the channels of pelucid bodies not directed or more hope in any one way than any other being equally pervious every way and according to these pores are more or greater in respect of the interstitial bodies the more transparent are the so constituted concretes and the smaller those pores are the weaker is the impulse of light communicated through them though the more quick be the progress upon this occasion I hope it will not be altogether unseasonable if I propound my conjectures hypotheses about the medium and conveyance of light I suppose then that the great part of the interstitia of the world that lies between the bodies of the sun and stars and the planets and the earth to be an exceeding fluid body very apt and ready to be moved and to communicate the motion of any one part to any other part though never so far distant nor do I much concern myself to determine what the figure of the particles of this exceedingly subtle fluid medium must be nor whether it have any interstitiated pores or vacuities it being sufficient to solve all the phenomena to suppose it an exceedingly fluid or the most fluid body in the world and yet impossible to determine the other difficulties that being so exceeding fluid a body it easily gives passage to all other bodies to move to and fro in it that it neither receives from any of its parts or from other bodies nor communicates to any of its parts or to any other body any impulse or motion in a direct line that is not of a determinate quickness and that when the motion is of such determinate swiftness it both receives and communicates or propagates an impulse or motion to any imaginable distance in straight lines with an unimaginable celerity and vigor that all kinds of solid bodies consist of pretty massive particles in respect of the particles of this fluid medium which in many places do so touch each other that none of this fluid medium interposes much after the same manner to use a gross similitude as a heap of great stones compose one great congeries or mass in the midst of the water that all fluid bodies which we may call tangible are nothing but some more subtle parts of those particles that serve to constitute all tangible bodies that the water and such other fluid bodies are nothing but a congeries of particles agitated or made fluid by it in the same manner as the particles of salt are agitated or made fluid by a parcel of water in which they are dissolved and subsiding to the bottom of it constitute a fluid body much more massive and dense and less fluid than the pure water itself that the air on the other side is a certain company of particles of quite another kind that is such as are very much smaller and more easily movable by the motion of this fluid medium much like those very subtle parts of cockenelle other very deep tinging bodies whereby a very small parcel of matter is able to tinge and diffuse itself over a very great quantity of the fluid disolvement or somewhat after the manner as smoke and such like minute bodies or streams are observed to tinge a very great quantity of air only this last similitude is deficient in one propriety and that is a perpetuity or continuance in that state of comixter with the air but the former does more nearly approach to the nature and manner of the airs being dissolved by this fluid or ether and this similitude will further hold in these proprieties that as those tinctures may be increased by certain bodies so may they be precipitated by others as I shall afterwards show it to be very probable that the like accidents happen even to the air itself further as these solutions and tinctures do alter the nature of these fluid bodies is to their aptness to propagate a motion or impulse through them even so does the particles of the air water and other fluid bodies and of glass crystal etcetera which are comixed with this bulk of the ether alter the motion of the propagated pulse of light that is where these more bulky particles are more plentiful and consequently a lesser quantity of the ether between them to be moved there the motion must necessarily be the swifter though not so robust which will produce those effects which I have I hope with some probability ascribed to it in the digression about colors at the end of the observations on muscovy glass now that other stones and those which have the closest and hardest textures and seem as far as we are able to discover with our eyes though helped with the best microscopes freest from pores are yet not withstanding replenished with them an instance will I suppose make more probable a very solid and unflawed piece of clear white marble if it be well polished and glazed has so curiously smooth surface that the best and most polished surface of any wrought glass seems not to the naked eye nor through a microscope to be more smooth and less porous and yet that this hard close body is replenished with abundance of pores I think these following experiments will sufficiently prove the first is that if you take such a piece and for a pretty while boil it in turpentine and oil of turpentine you shall find that the stone will be all imbued with it and whereas before it looked more white but more opacious now it will look more greasy but be much more transparent and if you let it lie but a little while and then break off a part of it you shall find the unctuous body to have penetrated it to such a determinate depth every way within the surface this may be yet easier tried with a piece of the same marble a little warmed in the fire and then a little pitcher tar melted on the top of it for these black bodies putting themselves into the invisible pores of the stone tinge it with so black a you that there can be no further doubt of the truth of this assertion that it abounds with small imperceptible pores now that other bodies will also sink into the pores of marble besides unctuous I have tried and found that a very blue tincture made in spirit of urine would very readily and easily sink into it as would also several tinctures drawn with spirit of wine nor is marble the only seemingly close stone which by other kinds of experiments may be found porous for I have by this kind of experiment on diverse other stones found much the same effect and in some indeed much more notable other stones I have found so porous microscope I could perceive several small winding holes much like wormholes as I have noted in some kind of per beck stone by looking on the surface of a piece newly flawed off for if otherwise the surface has been long exposed to the air or has been scraped with any tool those small caverns are filled with dust and disappear and to confirm this conjecture yet further I shall here insert an excellent account given into the Royal Society by the eminently learned physician Dr. Goddard of an experiment not less instructive than curious and accurate made by himself on a very hard and seemingly close stone called Oculus Mundi as I find it preserved in the records of that honourable society a small stone of the kind made by some authors Oculus Mundi being dry and cloudy weighed 5 and 209 over 256 grains the same put under water for a night and somewhat more become transparent and the superfaces being wiped dry weighed 6 and 3 over 256 grains the difference between these two weights 50 over 256 of a grain the same stone kept out of water one day and becoming cloudy again weighed 5 and 225 over 256 grains which was more than the first weight 16 over 256th of a grain the same being kept 2 days longer weighed 5 and 202 over 256 grains which was less than at first 7 over 256th of a grain being kept dry something longer it did not grow sensibly lighter being put under water for a night and becoming again transparent and wiped dry the weight was 6 and 3 over 256 grains the same with the first after putting it in water and more than the last weight after keeping of it dry 57 over 256th of a grain another stone of the same kind being variegated with milky white and grey like some sorts of agates while lay under water was always envired with little bubbles such as appear in water a little before boiling next to sides of the vessel there were also some like bubbles on the surface of the water just over it as if either some exhalations came out of it or that it did excite some fermentation in the parts of the water contiguous to it there was little sensible difference in the transparency of the stone before the putting under water and after to be sure the milky white parts continued as before but more difference in weight than in the former for whereas before the putting into the water the weight was 18 and 97 over 128 grains after it had lying in about 4 and 20 hours the weight was 20 and 27 over 128 grains so the difference was 1 in 58 over 128 grains the same stone was infused in the water scalding hot and so continued for a while after it was cold but got no more weight on infusing in the cold neither was there any sensible difference in the weight both times in which experiment there are three observables that seem very manifestly to prove the porousness of these seemingly close bodies the first is there acquiring a transparency and losing their whiteness after steeping in water which will seem the more strongly to argue it if what I have already said is about the making transparent or clarifying of some bodies as the white powder of beaten glass and the froth of some glutinous transparent liquor be well considered for thereby it will seem rational to think that this transparency arises from the insinuation of the water which has much the same refraction with such stony particles as may be discovered by sand viewed with a microscope which were formally replete with air that has a very differing refraction and consequently is very reflective which seems to be confirmed by the second observable namely the increase of weight after keeping and decrease upon drying and thirdly seem yet more sensibly confirmed by the multitude of bubbles in the last experiment we find also most acid salts very readily to dissolve and separate the parts of this body one from another which is yet a further argument to confirm the porousness of bodies and will serve as such to show that even glass also has an abundance of pores in it since there are several liquors that which long staying in the glass will so corrode and eat into it as at last to make it pervious of the liquor it contain of which I have seen very many instances since therefore we find by other proofs that many of those bodies which we think the most solid ones and appear so to our sight have not withstanding abundance of those grosser kinds of pores which will admit several kinds of liquors into them why should we not believe that glass and other transparent bodies abound with them we have many other arguments besides the propagation of light which seem to argue for it and whereas it may be objected that the propagation of light is no argument that there are those atomical pores in glass since there are hypotheses plausible enough to solve those phenomena by supposing the pulse only to be communicated through the transparent body to this I answer that that hypothesis which the industrious mercenas has published about the slower motion of the end of a ray in a denser medium then in a more rare and thin seems altogether insufficient to solve abundance of phenomena of which this is not the least considerable that it is impossible from that supposition that any colors should be generated from the refraction of the rays for since by that hypothesis indicating pulse is always carried perpendicular or at right angles with the ray or line of direction it follows that the stroke of the pulse of light after it has been once or twice refracted through a prism for example must affect the eye with the same kind of stroke as if it had not been refracted at all nor will it be enough for a defendant of that hypothesis to say that perhaps it is because the refractions have made the rays more weak or if so then two refractions in the two parallel sides of a quadrangular prism would produce colors but we have no such phenomenon produced there are several arguments that I could bring to events that there are in all transparent bodies such atomical pores and that there is such a fluid body as I am arguing for which is the medium or instrument by which the pulse of light is conveyed from the lucid body to the enlightened but that it being a digression from the observations I was recording about the pores of Ketteringstone it would be too much such if I should protract it too long therefore I shall proceed to the next observation End of Section 20 Section 21 of micrographia this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org Micrographia by Robert Hook Section 21 Observation 16 of charcoal or burnt vegetables charcoal or a vegetable burnt black affords an object no less pleasant than instructive for if you take a small round charcoal and break it short with your fingers you may perceive it to break with a very smooth and sleek surface almost like the surface of black ceiling wax this surface if it be looked on with an ordinary microscope does manifest abundance of those pores which are also visible to the eye in many kinds of wood ranged round the pith both in a kind of circular order and a radiant one with a multitude in the substance of the coal everywhere almost perforating and drilling it from end to end by means of which be the coal never so long you may easily blow through it and this you may presently find by wetting one end of it with spittle and blowing at the other but this is not all for besides these many great and conspicuous irregular spots or pores if a better microscope be made use of there will appear in infinite company of small and very regular pores so thick and so orderly set and so close to one another that they leave very little room or space between them to be filled with a solid body for the apparent interstitia or separating sides of these pores seems so thin in some places that the texture of a honeycomb cannot be more porous though this be not everywhere so the intercurrent partitions in some places being very much thicker in proportion to the holes most of these small pores seem to be pretty round and were ranged in rows that radiated from the pith to the bark they all of them seem to be continued open pores running the whole length of the stick and that they were all perforated I tried by breaking off a very thin sliver of the coal crosswise and then with my microscope diligently surveying them against the light for by that means I was able to see quite through them these pores were so exceedingly small and thick that in a line of them one eighteenth part of an inch long I found by numbering them no less than one hundred and fifty small pores and therefore in a line of them an inch long must be no less than twenty seven hundred pores and in a circular area of an inch diameter must be about five million seven hundred and twenty five thousand three hundred and fifty of the like pores so that a stick of an inch diameter may contain no less than seven hundred and twenty five thousand besides five million of pores the wood, I doubt not, seemed very incredible where not everyone left to believe his own eyes nay, having since examined caucus, black and green ebony lignum verte, etc I found that all these woods have their pores abundantly smaller than those of soft light wood in so much that those above Gauchachem seemed not above an eighth part of the bigness of the pores of peach but that the interstitia were thicker so prodigiously curious are the contrivances pipes or sluices by which the succus nutridius or juice of a vegetable is conveyed from place to place this observation seems to afford us the true reason for several phenomena of coals as first, why they look black and for this we need go no further than the scheme for certainly a body that has so many pores in it as this is discovered to have from Asia which no light is reflected must necessarily look black especially when the pores are somewhat bigger in proportion to the intervals than they are cut in the scheme, black being nothing else but a privation of light or a want of reflection and where so ever this reflecting quality is deficient there does that part look black whether it be from a porousness of the body as in this instance or in a deadening and dulling quality such as I have observed in the discordia of lead tin, silver, copper, etc next we may also as plainly see the reason of its shining quality and that is from the even breaking off of the stick, the solid inner tissue having a regular termination of surface and having a pretty strong reflecting quality than many small reflections become united to the naked eye and make a very pretty shining surface third, the reason of its hardness and brittleness seems evident for since all the watery or liquid substance that moistened and toughened these interstitia for the most solid parts are evaporated and removed, that which is left behind becomes of the nature almost of a stone which will not at all or very little bend without a diversion or solution of its continuity it is not my design at present to examine the use and mechanisms of these parts of wood that being more proper to another enquiry but rather to hint that from this experiment we may learn first what is the cause of the blackness of many burnt bodies which we may find to be nothing else but this that the heat of the fire agitating and rarifying the waterish, transparent and volatile water that is contained in them the continuation of that action does so totally expel and drive away all that which before filled the pores and was dispersed also through the solid mass of it and thereby caused a universal kind of transparency that it not only leaves all the pores empty but all the interstitia are also dry and opaque and perhaps also yet further perforated that that light only is reflected back which falls upon the very outward edges of the pores all they that enter into the pores of the body, never returning of being lost in it now that the charring or coaling of a body is nothing else may be easily believed by one that shall consider the means of its production which may be done after this or any such manner the body to be charred or cold may be put into a crucible, pot or any other vessel that will endure to be made red hot in the fire without breaking and then covered over with sand so as no part of it will be suffered to be open to the air then sent into a good fire and there kept till the sand continued red hot for a quarter, half or an hour or two or more according to the nature and bigness of the body to be cold or charred then taking it out of the fire and letting it stand till it be quite cold the body may be taken out of the sand while charred and cleansed of its water-ish parts but in the taking of it out care must be had that the sand be very near cold for else when it comes into the free air it will take fire and readily burn away this may be done also in any closed vessel or glass as a retort or the like and the several fluid substances which come over may be received in a fit recipient which will yet further continence this hypothesis and their manner of charring wood in great quantity comes much to the same thing namely an application of a great heat to the body and preserving it from the free excess of the devouring air this may be easily learned from the history of charring of coal most excellently described and published by that most accomplished gentleman in the 100-101-103 pages of his Silva to which I shall therefore refer the curious reader that desires a full information of it next we may learn what part of the wood it is that is the combustible matter for since we shall find that none or very little of those fluid substances that are driven over into the receiver are combustible and that most of that which is left behind is so it follows that the solid intertissure of the wood are the combustible matter further the reason why uncharred wood burns with a greater flame than that which is charred, as is evident because those waterish or volatile parts issuing out of the fired wood, every way not only shatter and open the body the better for the fire to enter but issuing out in vapors and wind they become like so many aliopiles or bellows whereby they blow and agitate the feared part and conduce to the more speedy and violent consumption or dissolution of the body third from the experiment of charring of coals whereby we see that notwithstanding the great heat and the duration of it the solid parts of the wood remain whilst they are preserved from the free access of the air anticipated we may learn that which has not that I know of been published or hinted nay, not so much as thought of by any and that in short is this first, that the air in which we live move and breathe and which encompasses very many and cherishes most bodies that encompasses that this air is the menstrual or universal disolvent of all sulfurous bodies second, that this action it performs not till the body be first sufficiently heated as we find requisite also to the dissolution of many other bodies by several other menstrus third, that this action of dissolution produces or generates a very great heat and that which we call fire and this is common also to many dissolutions of other bodies made by menstrus of which I could give multitudes of instances fourth, that this action is performed with so great a violence and does so manually act and rapidly agitate the smallest parts of the combustible matter that it produces in a diaphanous medium of the air the action or pulse of light which what it is I have elsewhere already shown fifthly, that the dissolution of sulfurous bodies is made by a substance inherent and mixed with the air that is like, if not the very same with that which is mixed in salt peter which by multitudes of experience that may be made with salt peter will I think most evidently be demonstrated sixthly, that this dissolution of bodies by the air a certain part is united and mixed or dissolved and turned into the air and made to fly up and down with it in the same manner as a metal line or other body dissolved into any menstrus does follow the motions and progress of that menstru until it be precipitated seventhly, that as there is one part that is dissolvable by the air so there are other parts with which the part of the air mixing and uniting to make a coagulum or precipitation as one may call it which causes it to be separated from the air but this precipitate is so light and in so small and rarefied or porous clusters that it is very volatile and is easily carried up by the motion of the air though afterwards when the heat and agitation that kept it rarefied ceases it easily condenses and commit with other indissolvable parts it sticks and adheres to the next body it meets with all and this is a certain salt that may be extracted out of soot eighthly, that many dissolvable parts are very apt and prompt to be rarefied and so, whilst they continue in that heat and agitation are lighter than the ambient air are thereby thrust and carried upward with great violence and by that means carry along with them not only that saline concrete I mentioned before but many terrestrial or indissolvable and rarefiable parts nay, many parts also which are dissolvable but which are not suffered to stay long enough in a sufficient heat to make them prompt and apt for that action and therefore we find in soot not only a part that being contained longer in a competent heat will be dissolved by the air or take fire and burn but a part also which is fixed, terrestrial and irrefirable ninth, that there are as these several parts that will rarefied and fly or be driven up by the heat so are there many others that are irrefutable by the aerial minstrum so are they of such sluggish and gross parts that they are not easily rarefied by heat and therefore cannot be raised by it the volatility or fixness of a body seeming to consist only in this that the one is of a texture or has component parts that will be easily rarefied into the form of air and the other that it has such as will not without much ado be brought to such a constitution and this is that part which remains behind in a white body called ashes which contains a substance or salt which chemists call acolyte what the particular natures of each of these bodies are I shall not hear examined intending it in another place but shall rather add that this hypothesis does so exactly agree with all phenomena of fire and so genuinely explicate each particular substance that I have hitherto observed that it is more than probable that this cause which I have assigned is the true, adequate, real and only cause of these phenomena and therefore I shall proceed a little further to show the nature and use of the air tensely, therefore the dissolving parts of the air are but few that is, it seems of the nature of those saline menstruums or spirits that have very much flag me mixed with the spirits and therefore a small parcel of it is quickly glutted and will dissolve no more and therefore unless some fresh part of this menstruum be applied to the body to be dissolved the action ceases and the body leaves to be dissolved and to shine which is the indication of it though placed or kept in the greatest heat whereby saltpeter is a menstruum when melted and red hot that abounds more with these dissolved particles and therefore is a small quantity of it will dissolve a great sulfurous body so will the dissolution be very quick and violent therefore in the 11th place it is observable that as in other solutions if a copious and quick supply of fresh menstruum though but weak be poured on or applied to the dissolvable body it quickly consumes it so this menstruum of the air if by bellows or any other such contrivance it be copiously applied to the shining body is found to dissolve it as soon and as violently as the more strong menstruum of melted nitra therefore 12thly it seems reasonable to think that there is no such thing as an element of fire that should attract or draw up the flame or toward which the flame should endeavor to ascend out of a desire or appetite of uniting with that or primitive and generating element but that that shining transient body which we call flame is nothing else but a mixture of air and volatile sulfurous parts of dissolvable or combustible bodies which are acting upon each other whilst they ascend that is flame seems to be a mixture of air and the combustible volatile parts of any body which partially encompassing air does dissolve or work upon which action as it does intend the heat of the aerial parts of the dissolvent so does it thereby further graphify these parts that are acting or that are very near them whereby they growing much lighter than the heavy parts of that menstruum that are more remote are thereby protruded and driven upward and this may be easily observed also in dissolution made by any other menstruum especially such as either create heat or bubbles now this action of the menstruum or air on the dissolvable parts is made with such violence or is such that it impart such motion and pulse to the diaphanous parts of the air as I have elsewhere shown is requisite to produce light this hypothesis I have endeavored to raise from an infinite of observation and experiments the process of which would be much too long to be here inserted and will perhaps another time afford matter copious enough for a much larger discourse the air being a subject which though all the world has hitherto lived and breathed in and been very unconversed about has yet been so little truly examined or explained the diligent inquirer will be able to find but very little information from that which has been, till of late, written of it but being once well understood it will, I doubt not enable a man to render an intelligible nay probable, if not the true reason of all the phenomena of fire which as it has been found by writers and philosophers of all ages a matter of no small difficulty as may be sufficiently understood by their strange hypotheses and unintelligible solutions of some few phenomena of it so it will approve a matter of no small concern and use in humane affairs as I shall elsewhere endeavour to manifest when I come to show the use of the air in respiration and for the preservation of the life, nay for the conservation and restoration of the health and natural constitution of mankind as well as all other aerial animals and also the uses of this principle or property of the air in chemical mechanical and other operations in this place I have only time to hint a hypothesis which if God permit me life and opportunity I may elsewhere prosecute, improve, and publish in the meantime, before I finish this discourse I must not forget to acquaint the reader that having had the liberty granted me of making some trials on a piece of Lignum falsely shown to the Royal Society by the eminent and genius and learned physician Dr. Int who received it for a present from the famous Ingenioso Caballero de Ponzi it to being one of the fairest and best pieces of the Lignum falsely he had seen having, I say, taken a small piece of this wood and examined it I found it to burn in the open air almost like other wood and instead of a resinous smoke or fume it yielded a very bituminous one smelling much of that kind of scent but that which I chiefly took notice of was that cutting off a small piece of it about the bigness of my thumb and charring it in a crucible with sand after the manner I above prescribed I found it infinitely to abound with the smallest sort of pores so extremely thick and so regularly perforating the substance of it long ways that breaking it off across I found it to look very like a honeycomb but as for any of the second or bigger kind of pores I could not find that it had any so that it seems whatever was the cause of its production it was not without those small kinds of pores which we have only hitherto found in vegetable bodies and comparing them with the pores which I found in the charcoal that I by this means made of several other kinds of wood I find it resembled none so much as those of fire to which it is not much unlike in grain also and several other properties and therefore whatever is by some who have written of it and particularly by Francisco Staluto wrote a treatise in Italian of that subject which was printed in Rome 1637 affirmed that it is a certain kind of clay or earth which in tractive time has turned into wood I rather suspect to quite contrary than it was at first certain great trees of fur or pine which by some earthquake or other casualty came to be buried under the earth and was there after a long time's residence according to the several natures of the encompassing adjacent parts either rotted and turned into a kind of clay or petrified and turned into a kind of stone or else had its pores filled with certain mineral juices which being stayed in them and in tractive time coagulated appeared upon cleaving out fires or else from some flames or scorching forms that are the occasion off times and usually accompany earthquakes might be blasted and turned into coal or else from certain subterraneous fires which are affirmed by that author to abound much about those parts namely in a province of Italy called Umbria now the Duchy of Spolato in the territory of Todi anciently called Tudor and between the two villages of Colosseco and Rosaro not far distant from the highway leading to Rome where it is found in greater quantity than elsewhere are by reason of their being encompassed with earth and so kept close from the dissolving air charred and converted into coal it would be too long a work to describe the several kinds of pores which I met with all and by this means discovered in several other vegetable bodies nor is it my present design to expatiate upon instances of the same kind but rather to give a specimen of as many kinds as I've had opportunity as yet of observing reserving the prosecution and enlarging on particulars to a more fit opportunity and in prosecution of this design I shall here add end of section 21 recording by Todd section 22 of micrographia this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Larry Wilson micrographia by Robert Hook observation 17 a petrified wood and other petrified bodies of this sort of substance I observed several pieces of very differing kinds both for their outward shape color grain texture hardness etc some being brown and reddish others gray like a home others black and flint like some soft like a slate or whetstone others as hard as a flint and as brittle that which I more particular examined was a piece about the bigness of a man's hand which seemed to have been a part of some large tree that by rottenness had been broken off from it before it began to be petrified and indeed all that I have yet seen seemed to have been rotten wood before the petrification was begun a not long since examining and viewing a huge great oak that seemed with mere age to be rotten as it stood I was very much confirmed in this opinion for I found that the grain color and shape of the wood was exactly like this petrified substance and with a microscope I found that all those microscopical pores which in sappy or firm in sound wood are filled with the natural or innate juices of those vegetables in this they were all empty like those of vegetables charred but with this difference then I have seen in any charcoals may even in those of coals made of great blocks of timber which are commonly called old coals the reason of which difference may probably be that the charring of vegetables being an operation quickly performed and whilst the wood is sappy the more solid parts may more easily shrink together and contract the pores or interstitia between them then in rotten wood where that natural juice seems only washed away by adventitious or unnatural moisture and so though the material may be wasted from beneath the firm parts yet those parts are kept asunder by adventitious moistures and so by degrees settled in those postures and this I likewise found in the petrified wood that the pores were somewhat bigger than those of charcoal each pore being near up a half as big again but they did not bear the disproportion which is expressed in the tenth scheme between the small specks or pores in the first figure which represented the pores of coal or wood charred and the black spots of the second figure which represent like microscopical pores in the petrified wood where these last were drawn by a microscope that magnified the object over six times more in diameter than the microscope by which those pores of coal were observed now though they were a little bigger did they keep the exact figure and order of pores of coals and of rotten wood which last also were much of the same size the other observations on this petrified substance that a while since by the appointment of the Royal Society I made and presented to them an account of were these that follow which had the honor done them by the most accomplished Mr. Evelyn my highly honored friend to be inserted and published among those excellent observations wherewith his Silva was replenished and would therefore have been here omitted had not the figure of them as they appeared through the microscope been before that engraven this petrified substance resembled wood in that first all the parts of it seem not at all dislocated or altered from their natural position whilst they were wood but the whole piece retained the exact shape of wood having many of the conspicuous pores of wood still remaining pores and showing a manifest difference visible enough between the grain of the wood and that of the bark especially when any side of it was cut smooth and polite for then it appeared to have a very lovely grain like that of some curious close wood next it resembled wood in that all the smaller and if I may so call those which are only visible with a good magnifying glass microscopical pores of it appear both when the substance is cut and polished transversely and parallel to the pores of it perfectly like the microscopical pores of several kinds of wood especially like and equal to those of several sorts of rotten wood which I have since observed retaining both the shape, position and magnitude of such pores it was differing from wood first in weight being to common water as three and a quarter to one whereas there are few of our English woods that when very drier found to be full as heavy second in hardness being very near as hard as flint and in some places of it also resembling the grain of a flint and like it would very readily cut glass and would not without difficulty especially in some parts of it be scratched by a black hard flint it would also as readily strike fire against a steel or against a flint as any common flint thirdly in the closeness of it for though all the microscopical pores of this petrified substance were very conspicuous in one position yet by altering that position of the polished surface to the light it was also manifest that those pores appear darker than the rest of the body only because they were filled up with a more dusky substance and not because they were hollow fourthly in it's incombustableness in that it would not burn in the fire may though I kept it a good while red hot in the flame made very intense by the blast of a small pipe and a large charcoal yet it seemed not at all to have diminished its extension but only I found it to have changed its color and to appear of a more dark and dusky brown color nor could I perceive that those parts which seem to have been wood at first were anything wasted but the parts appeared as solid and close as before it was further observed also that as it did not consume like wood neither did it crack and fly like a flint or such like hard stone nor was it long before it appeared red hot fifthly it's disolubleness for putting some drops of distilled vinegar upon the stone I found it presently to yield very many bubbles just like those which may be observed in spirit of vinegar when it corrodes corals though perhaps many of those small bubbles might proceed from some small parcels of air which were driven out of the pores of this petrified substance by the insinuating liquid menstrual sixthly in its rigidness and friability being not at all flexible but brittle like a flint in so much that I could with one knock of a hammer break off a piece of it and with a few more reduce it into a pretty fine powder seventhly it seemed also very differing from wood to the touch feeling more cold than wood usually and much like other close stones and minerals the reasons of all which phenomena seem to be the petrified wood having lain in some place where it was well soaked with petrifying water that is such a water as is well impregnated with stony and earthy particles did by degree separate either by straining and filtration or perhaps by precipitation cohesion and coagulation abundance of stony particles from the permeating water which stony particles being by means of the fluid vehicle conveyed not only into the microscopical pores and so perfectly stopping them but also into the pores or interstitia by which may perhaps be even in the texture or schematics may of that part of the wood which through the microscope appears most solid do thereby so augment the weight of the wood as to make it above three times heavier than water and perhaps six times as heavy as it was when would next they thereby so lock up and feather the parts of the wood that the fire cannot easily make them fly away but the action of the fire upon them is only able to char those parts as it were like a piece of wood if it be closed very fast up in clay and kept a good while red hot in the fire will by the heat of the fire be charred and not consumed which may perhaps also be somewhat of the cause why the petrified substance appeared of a dark brown color after it had been burnt by this intrusion of the petrifying particles this substance also becomes hard and friable and in the smaller pores of the wood being perfectly wedged and stuffed up with those stony particles the small parts of the wood have no place or pores into which they may slide upon bending and consequently little or no flexion or yielding it all can be caused in such a substance the remaining particles likewise of the wood among the stony particles may keep them from cracking and flying when put into the fire as they are very apt to do in a flint nor is wood the only substance that may by this kind of transportation be changed into stone for I myself has seen and examined it very many kinds of substances and among very credible authors we may meet with histories of such metamorphoses wrought almost on all kinds of substances both vegetable and animal which histories it is not my business at present either to relate or epitomize but only to set down some observation I'd lately made on several kind of petrified shell found about kinsham which lies within four or five miles of Bristol which are commonly called serpentine stones examining several of these very curiously figured bodies which are commonly thought to be stones formed by some extraordinary plastic virtue latent in the earth itself I took notice of these particulars first that these figured bodies are stones were a very different substances as to hardness some of clay some of moral some of soft stone almost all of the hardness of those soft stones which mason's call fire stone others as hardest Portland stone others as hardest marble and some as hardest flint or crystal next they were a very different substances as to transparency color some white some almost black some metaline or like marco sites some transparent like white marble others like flawed crystal some gray some diverse colors some radiated like those long petrified drops which are commonly found at the peak and in other subterraneous caverns which have a kind of pith in the middle thirdly that they were very different as to the manner of their outward figuration or some of them seem to have been the substance that had filled the shell of some kind of shellfish others to have been the substance that had contained or enwrapped one of those shells on both which the perfect impression either of the inside or outside of such shells seems to be left but for the most part those impressions seem to be made by an imperfect or broken shell the great end or mouth of the shell being always wanting and oftentimes the little in and sometimes half and in some there were impressions just as if they had been holes broken in the figurating imprinting or molding shell some of them seem to be made by such a shell very much bruised or flawed in so much that one would verily have thought that very figured stone had been broken or bruised while said jelly were twir and so hardened but within the grain of the stone there appeared not the least sign of any such bruise or breaking but only on the very uttermost superficies fourthly they were very different as to their outward covering some having the perfect shell both in figure color and substance sticking on upon its surface and adhering to it but might very easily be separated from it and like other common cockle or scallop shells which some of them most accurately resembled were very disolvable in common vinegar others of them especially those serpentine or helical stones were covered or retained the shining or pearl colored substance of the inside of a shell which substance on some parts of them was exceeding thin and might very easily be rubbed off on other parts was pretty thick and retained a white coat or flaky substance on top just like the outside of such shells some of them had very large pieces of the shell very plainly sticking onto them which were easily to be broken or flaked off by degrees they likewise some of them retained all along the surface of them very pretty kind of sutures such as are observed in the skulls of several kinds of living creatures which sutures were most curiously shaped in the manner of leaves and every one of them in the same shell exactly like one another which I was able to discover plainly enough with my naked eye but more perfectly and distinctly with my microscope all these sutures by breaking some of these stones I found to be termini or boundaries of certain diaphragms or partitions which seemed to divide the cavity of the shell into a multitude of very proportionate and regular cells or caverns these diaphragms in many of them I found very perfect and complete of a very distinct substance from that which filled the cavities and exactly the same kind with that which covered the outside being for the most part whiteish or mother of pearl color as for the cavities between those diaphragms I found some of them filled with marble and others with several kinds of stones others for the most part hollow only the whole cavity was usually covered over with a kind of tartarious petrified substance which stuck about the sides and was there shot into every curious regular figures just as tartar or other dissolved salts are observed to stick and crystallize about the size of the containing vessels or like those little diamonds which I before observed to have covered the vault cavity of a flint others had these cavities all lined with a kind of metaline or a macrocyte like substance which with a microscope I could as plainly see most curiously and regularly figured as I had done those in a flint from all which and several other particulars which I observed I cannot but think that all these and most other kinds of stony bodies which are found thus strangely figured follow their formation and figuration not to any kind of plastic virtue inherent in the earth but to the shells of certain shellfishes which either by some deluge inundation earthquake or some such other means came to be thrown to that place and there be filled with some kind of mud or clay or petrified water or some other substance which in tracts of time has been settled together and hardened in those shelly molds and shaped substances we now find them that the great and thin end of these shells by that earthquake or whatever other extraordinary cause it was that brought them thither was broken off and that many others were otherwise broken, bruised and disfigured that these shells which are thus spiral and separated with diaphragms were some kind of not a lie or porcelain shells and that others were shells of cockles muscles, periwinkles, scallops etc of various sorts that these shells and many from the particular nature of the containing or enclosed earth or some other cause have in tracts of time rotted and molded away and only left their impressions both on the containing and contained substances and so left them pretty loose one within another so that they may be easily separated by a knock or two of a hammer that others of these shells adjacent to them have by a long continuance in that posture been petrified and turned into the nature of stone just as I even now observe several sorts of wood to be that often times the shell may be found with one kind of substance within and quite another without having perhaps been filled in one place and afterwards translated to another which I have very frequently observed in cockle muscle, periwinkle and other shells which I have found by the seaside nay, further that some parts of the same shell may be filled in one place and some other caverns in another and others in a third or fourth or fifth place for so many differing substances have I found in one of these petrified shells and perhaps all these differing from the encompassing earth or stone that means how all which varieties may be caused I think will not be difficult to conceive to anyone that has taken notice of those shells which are commonly found on the seashore and he that shall thoroughly examine several kinds of such curiously formed stones will I am very apt to think find reason to suppose their generation or formation to be ascribable to some such accidents as I have mentioned and not to any plastic virtue for it seems to me quite contrary to the infinite prudence in nature which is observable in all its works and productions to design everything to a determinate end and for the attaining of that end makes use of such ways as are as far as the knowledge of man has yet been able to reach altogether consonant and most agreeable to man's reason and of no way or means that does contradict or is contrary to humane racialization whence it has a long time been a general observation and maxim that nature does nothing in vain it seems I say contrary to that great wisdom of nature that these prettily shaped bodies should have all those curious figures and contrivances which many of them are adorned and contrived with generated a rot by a plastic virtue for no higher end than only to exhibit such a form which he that shall thoroughly consider all circumstances of such kind of figured bodies will I think reason to believe though I confess one cannot presently be able to find out what nature's designs are it were therefore very desirable that a good collection of such kind of figured stones were collected and as many particulars, circumstances and informations collected with them as could be obtained that from such a history of observations well-ranged examined and digested the true original a production of all those kinds of stones might be perfectly surely known such are thunderstorms, lapides telleries lapides judica and multitudes of other where I've mentioned is made in Aldenandes Wyrmias and other writers and minerals. End of section 22