Ethylid 77 i thylid - Nitrate. 199 
a 
e (001) A e (011) = 69° -2’ 
e (001) A @ (111) = 78° 35’ 
d (111) A d'(111) = 60° 50’ 
From these angles the elements of the crystals were calculated, 
l 
c:6: & = 4°32645 : 1°65788 : 1°00000 
B = 89° 43’ 52” 
Sade important angles, calculated from the same data, are as 
¢ (001) ~A.¢g G1). =. 78. = 
g G11) A g'fill) = +=60° 56’ 
@(ill) qj g (1) = 114° 17 
d (111) A e (011) = 66°18’ 
g (111) A € (011) = 65° 35’ 
d@ (111) A e'(011) = 122° 56’ 
g (111) A e(011) = 122° 48’ 
d (111) A 5 (010) = 59° 35’ 
g (111) A (010) = 59° 32’ 
The measured angles agreed quite closely with the calculated 
angles when the character of the planes was such as to admit 
of satisfactory observations. This will be seen from the follow- 
ing oy ey lagi the angles measured on different crystals 
or da 
pp mip nae 5 per 60°46’, 60°47’, 60°51’, 60°52’, 60°50’, e 
¢ Ad=78°35', 78°39’, 78°40", 78°33’, 78°34’, 78°40’, 78°38’, 13°36, 
ete. 
In many cases, hbsaedvee. the or were by no means er 
factory, being generally polishe and yet far from smooth, 
hence the reflections given b them were more or less faba 
tain. The planes g, g’ were quite rage striated, and hence 
the measurements made upon them were always unreliable. 
The following angles were all obtained tro a single crystal ; 
the wide variations from the calculated angles observed in some 
cases are due to the cause nam 
peer: 97' cigeue 12’ dad= 60° 46’ 
6 AGg=78° 38’ Gag=aNe. 7 g Ag’= 60° 46 
€ Ag =78° 10’ d Ac = 65° 52 gae= 65° 41’ 
€ Ag’=78° 30 d' Ac'= 66° 23' Ae= 66° 33’ 
} ce Ae =69° 3’ & Ae'==122° 51’ g Ae=122° 57 
c' Ae = 69° 2! BAe == 122° 30’ J A€ =1238° 33’ 
