CALCITES OF NEW YORK 63





Edge X


Edge Y


Edg


:eZ


measured


81 53


35 26


33


7


calculated


81 34 2S


35 29 57


33


17



42

The corresponding angular values for 1^ (39.15.55.8) and S' (15.7.22.2)
are as follows:

EdgeX Edge Y Edg^Z

39.15.54.8 measured 87 15 30 39 34 ' 59



calculated


87


14 i


30


46 i-


34


25


15.7.22.2 measured






37


14


25


22


calculated


83


50


36


5


25


33



From this it will be seen that the edge Y of (15.7.22.2) and the edge
Z of (39.15.55.8) are respectively close to the edges Y and Z of 2RV of
Hessenberg and that both of the former forms which were determined from
the averaging of a number of readings for every angle agree closely with the
theoretical values. The scalenohedron I^ (39.15.55.8) which is new to the
species lies closer to the zone [62S1.1101] than 2RV-- The Naumann
symbols for these substituted forms are:

39.15.54.8 = 3R^ and
15.7.22.2 = 4R^

Prisms. The prism b (lOTO) occurs as a series of bright, sharply defined
faces in the rhombohedral zone well developed in habit. The prism a was
noted as a series of very narrow planes beveling the basal edges of 3; (62Sl)
and principally observed in measuring the zone [202T.0221] on crystal 10.
Pyramid. The pyramid y(8.8.T6.3) is present lying, in zone between
(2131) and the new negative scalenohedron (4.6. TO. 1). The faces are narrow
but very brilliant and susceptible of exact determination.
