LE. 8. Dana—Stibnite from Tapan. 219 
stibnites was made more difficult in consequence of the irregu- 
larity which has just been described. Many crystals of fault- 
less luster, which seemed capable of giving excellent angles, 
were found to be quite unreliable because of an incipient bend- 
ing of the character described. In cases where this difficulty 
did not exist the results were very satisfactory. A number of 
erystals were subjected to careful measurement and the results 
obtained from the best one of these deserve to be stated in de- 
tail. It showed the planes p(111), (843), 7(853) and w,(5-10°3), 
all giving excellent reflections ; there were also present several 
smaller planes and a number of prisms, but they did not give 
results accurate enough to serve the purpose in view. As fun- 
damental (supplement) angles were obtained 
353 ~ 353==99° 39’ 0” and 353 ~. 353=55° 1’ 0" 
The following comparison between the measured angles and 
those calculated from the above data will show that the angles 
ass re as accurate as could be expected, and that the 
crystal is unusually free from irregularity. 
Meas- Calcu- Meas- Calen- 
tL 111 10° 48). 5, U1, ill ny eer ; 
ML Til 70° 49° “gnc! 11, iil 71° 231 tn = 
a aCe ee ee 
353 ~ 35 3 x éiaae i 
= 8 99° 39” $00" 30” 353 358 : = : y tsse1 
5-103 BI08 ere t 119° 27” as Sep 2408 BI? 34” t bi say’ 
iH She 4 ae! wt t 110° 38” pes = ae : 126° 28” 
MHS US Sty SOSA FTDS 180027} 
The above measurements show that a considerable degree of 
confidence may be placed in the axial ratio deduced from the 
fundamental angles selected. This is 
a:b: 0 = 1: 100749; 102550. 
The prismatic angle JJ (110. 110)=89° 34’. 
The axial ratio obtained by Krenner differs somewhat from 
this, he giving— 
111. 111=70° 334 111, 111=71° 3976, and 110 110=89° 5”8. 
The following is a list of the planes which have been ob- 
Served on the Japanese stibnite, those which are new being 
te by an asterisk (") The planes are given in the order 
of the vertical zones in which they oceur: 
