( 1044 ) 
For het 
sin? V = 
‚ becomes: 
cos? 40°44 ZO" 
cot 2331! 120)" gin De 36! 26" sindO” 44! 20e 08° 65 | iy 47" sin 6® 19 47"'sin*40. 44'20" 
from which 
V = 47°4' round «; 2 V = 58°52" round a as bisectrix. 
a ‘ 275° 
= [== ae 
PEEN EE 
i | RSE NE EB EEE AE asann 
ENE 
f HN ba HH + | a EE Ds HHH Ht EEH 
HH EH 
Et Ei EN EEE: EEE 
AW Nasibelecisss HEEE 
EEE 
|. 
En Sn 
HEEE 
H 
HH 
. 
aH 
AHHH 
as 
briana si 
Att 
BEE 
B 
maan 
zj 
a 
if 
HH 
ie 
a 
B oe is ae EEE 
ek a 
é a! 
ie 
SE eee era errr etree 
SSE ns 
88 
di Gen a 
ee 
a ae 
fo a zi = 
Mig, 6. 
From this appears at the same time that the mineral is optically 
negative. 
By a graphical method the axial-angle can easily be determined 
from y. Fig.6 gives the curves y= 78° for different values of V 
(comp. fig. 4). In the diagram the pole of S(e=116°48’, s=40°44’) 
lies between the eurves for WV = 40° and V=50°, and in a place, 
which, as appears from interpolation, corresponds to about |” = 47° 
This latter value gives consequently half the axial-angle of the 
amphibole. 
Attention should be paid to the fact that this method furnishes 
