486 
PK0FES80E IIFNEY A. MIFES : AY EYQUIEY INTO 
The following are exain})les of nieasnieiueiits iii)on them :— 
ZiYC Snlphate ; prism zone; m = M = {HO}, B = (010], A = {100}. 
On the following day :— 
r f 187° 10', 
I\I -j 
186° 
42', 
1 
186° 
39', 
OO 
0 
24', 
i 
I 
' 97° 
53', 
m] 
J.8G° 
41', 
m 
. 97° 
21', 
m < 
' 97° 
56', 
Bi 
' 52° 
16', 
Bm = 
45° 
41' to 45° 
9', 
. 97° 
53', 
Bm 
= 45° 
37'to 45° 34', 
. 52° 
8', 
B = 
52° 
12', 
B 
52° 
19', 
BM' 
= 45° 38' „ 45° 33', 
M'< 
. qO 
41', 
BM' = 
45° 
31' to 45° 
33', 
A/ru 
} G° 
41', 
1 
= 45° 
37'. 
1 
6° 
39'., 
A' = 
322° 
18'. 
iVi < 
L G° 
36', 
A' « 
' 322° 
19', 
rii' 
277° 
5G', 
322° 
17', 
_B' 
232° 
19', 
'277° 
56', 
277° 
52', 
m 
277° 
25', 
,277° 
19', 
The value generally given for the prism angle of zinc snlphate is 91 12 , in the 
above crystal various vicinal prism forms are indicated, the angles ol which would 
range from 91° G to 91° 15' even for the best faces. 
Magnesium Snlphate; prism zone; ni — M — {HO}. 
8.20 r.M. ; t = 1G’5°. 
12° 30V, 
jn 282° 59'. 
9.30 P.M. ; t = 1G‘5°. 
~m 102° 49' above zone, 
M 12° 32', 
m' 283° 8^^', three images in vertical plane, 
i M' 192° 2Gh' below zone. 
