E. 8. Dana—Chondrodite from the Tilly-Foster Iron Mine. 99 
considered, it will be seen that the hemihedrism is like that in 
the other case, except that p* is holohedral. For macrodomes 
there are 2'(2-7=028), 1?(1-72=011), 23(2-7=021), 24(47=041) ; 
the last has not been observed on humite. On measuring the 
planes below, it was found that they were not distributed as was 
expected in accordance with the monoclinic character of the 
crystal; instead, either extremity of the brachydiagonal axis 
was differently developed. There are present also at one ex- 
tremity + ¢'(4-7=407), though the plane could be only approxi- 
mately measured. This is probably also to be explained as 
having resulted from a revolution parallel to the basal plane. 
The crystal was very small and not at all adapted to ex- 
periments having in view the discovery of any proper hemi- 
morphic development. Some of the angles measured on both 
these crystals are contained in the preceding table. 
Unfortunately the inclination to Con no one of the pyrami- 
dal planes could be measured with perfect accuracy ; the meas- 
urements are good, yet not entirely trustworthy. These planes, 
though brilliant, are uniformly fractured in the manner already 
explained, and this made all the angles a little uncertain. 
The caleulated angles as given have as their basis the prismatic 
angle I, /=94° 44’ 14”" and the macrodome angle (A 12?=144° 
45° 11”, following the analogy of humite in which the vertical 
axes of types If and III have the ratio 10 to 9. 
The corresponding parameters are: 
a (vert.)=1°41512; B=1; c=1-08630. 
Very little further can be said in regard to the crystals of the 
3d type. Those observed had a somewhat different color from 
those of type II; that is, the color was more yellowish, less o 
a pure garnet-red—though this may be accidental. No analy- 
sis was possible of course. The method of occurrence was 
much like that of the brilliant crystals of the second type; and 
the associated minerals were the same, with, probably as a later 
formation, brucite. 
8. Description of Crystals of Type I. 
The occurrence of large coarse crystals of quite impure chon- 
drodite, imbedded in the massive material, has already been de- 
scribed. These belong, at least in part, to the first of Scacchi’s 
types. As has been remarked, the crystals of this character do 
