of the Primitive Crystal of the Sulphate of Barytes • 309 
In conclusion, it may be observed that two motives induced me 
to offer this communication to the Geological Society. One, that it 
may assist in arranging the series of crystals; the other, that it 
may serve as material for the geometrician in the calculation of the 
precise angles which the planes of the several modifications form 
with each other and with those of the primitive crystal ; the acute 
angle of the latter, being (according to the reflecting goniometer) 
78° 18', the obtuse 101° 42/, and a lateral or a terminal plane 90°. 
Table of Measurements . 
1 
By W. P 
According to Haiiy. 
' A - ’ s 
1 
Oil 
P 
tr | 
fa 
2 
90° 

1 
— 
P' 
or 
P" 
— 
140° 
50' 
140° 
46' 
6" 
s 
on 
M 
PI. 
xxv. Fig 
.110 
* 
2 
— 
P' 
or 
P" 

3 
166° 
— 
169° 
19' 
45" 
30'" t 
Oil 
M 
. — 
117 
* 
2 
— 
1 

20 
1 53° 

151° 
26' 
21" 
t 
on 
s 
. — 
— 
* 
2 
— 
2 
- — 
3 
126° 

3 
— 
P 

— 
12 1° 
55' 
3 
— 
1 

20 
148° 
10' 
3 
— 
3 
— 
4 
116° 
25' 
4 
— 
P 
— 
5 
1 4l 0 
10' 
o 
o 
59' 
21" 
d 
on 
P 
# 
, — 
109 
4 

1 
___ 
20 
128 
50' 
4 
— 
3 

— 
160 
40' 
4 
, 
4 
— 
5 
77 
40' 
78° 
V 
18" 
d 
on 
d 
# 
. — 
108 
4 
— 
5 
__ 
20 
163° 
4P 
* 
5 
— 
P 
— 
6 
16 1° 
162° 
2' 
44" 
r 
on 
P 
. 
114 
* 
5 

5 
— 
— 
44° 
50' 
* 
5 
— 
6 
— 
20 
167° 
— 
* 
6 
— 
P 

7 
173° 

9 
— 
P 

10 
90° 
— 
90° 
k 
on 
P 
* 
. — 
115 
9 
— 
P' 
— 
10 
128° 
55' 
129° 
13' 
54" 
k 
on 
M 
# 
. — 
111 
* 
10 
— 
P' 
__ 
11 
160° 

* 
10 
— 
9 

20 
153° 

12 
— 
P 
— 
13 
12 7° 
12' 
127° 
5' 
13" 
o 
on 
P 
# 
. __ 
112 
12 
— 
14 
— 
20 
155° 
— 
13 
— 
P 
— 
14 
11 0° 
SO' 
13 

P 
— 
- 
141° 
— . 
* 
14 
— 
P 
— 
15 
124° 
— 
14 

P 

_ 
154° 
— 
16 
— 
P 
— 
17 
143° 
— 
* 
16 

P 
- 
— 
126° 
— 
17 
P 
— 
_ 
115° 
30' 
115° 
33' 
8" 
2 
on 
P 
. — 
118 
* 
18 
— 
P 
— 
19 
125° 
0 
■ V, 
