92 EF. S Dana—Chondrodite from the Tilly-Foster Iron Mine. 
The fundamental form employed is the same as that adopted 
in Dana’s Mineralogy ; for the reasons for retaining it, as also 
its relation to those of other authors, reference must be made to 
the complete memoir. The letters used are those of Scacchi, 
with this change, that for the planes of the third type the cor- 
responding Greek letters, and for the first type the correspond- 
ing capital letters, are employed. 
Taste I. Taste IIL 
A= 0(001). , C = +7 (010). 
Calcu- Calenu- 
lated. I. WN Tita IL. IIL. IV. 
) 11-4 1011/57° 33” ° gg7| .uatiet 
@ |1-2lo1157° 337) 57° 28 BY 401150. os 
2 
e@ |= 20530 4 90 
2 
él zx 203/43 583 90 
je? |2-% \201\70 57 90 
4 
= Sig 44 404) ,,. 50 «7 | {50° 13’%lnn0 yo 
1 \--9\947 4” \44° 2 
nie 46 41 |e go |e? B0’faa> an’|]50 1s |4 5) 4 15D 30 (oO 3 
he 
rm |e-2)245154 10 64 12 42 34| 42 39| 42 32 (42 36 
4 si §66 39 33 31 
vd 32|243|66 34 166 32 (66 26 66 35 | |33 32 133 3g |. 33 30 |88 20 
rt |4-2i241/81 47 | 81 52 25 6 0 
. 135 574 
1 2 5 
n 3 223/54 56 44 14} “ua Th 
m | 2 |221/76 50 52 58 
mi 6-5 641 84 40 54 16 54 18 
In tables II and IT are given the angles on A and C as meas- 
ured in a series of crystals here numbered II, III, 1V. (The 
measured angles of other crystals are given in the memoir.) 
They are important as showing how far the angles are constant. 
Some considerable variations from calculated angles in a few 
nes. 
_ Of the planes which occur, according to bee and vom 
Rath, on type II of humite, I have identified all but m of Scac- 
chi ($-) and 3-e of vom Rath (¢-7). Of new planes I have found 
