ME, H. J. BEOOKE ON THE GEOMETEICAL ISOMOEPHISM OE CETSTALS. 41 
agreeing angles in the range between 55° and 58° than in the others, the elementary 
angle of 57° 30' of Hematite has been adopted as the elementary type. 
Now Hematite may be associated with Quartz by the angles — 
Hematite 75° 42', Quartz 75° 18', 
Hematite 82 44, 
and with Calcite by the angles — 
Hematite 38° 7', 
Hematite 44 27, 
Quartz 82 31, 
Calcite 38° 17', 
Calcite 44 37, 
forming a small plesiomorphous group, with which other individuals and other groups 
have been successively connected, so as to reduce the entire system to a single plesio- 
morphous group of nearly equal angles, as shown in Table E, 2. 
To exhibit the effect of this grouping upon Hematite, Quartz, and Calcite, the Table T 
has been framed, by first assuming new primary forms for Quartz and Calcite, then trans- 
ferring to each of the three minerals the symbols of the other two, and then calculating 
in each case the angles corresponding to the transferred symbols. 
Symbols 
common to 
T. 
Corresponding Angles of 
Symbols 
common to 
T. 
Corresponding Angles of 
Hematite. 
Quartz. 
Calcite. 
Hematite. 
Quartz. 
Calcite. 
6 
5 
5 
O 
3 
36 
O 
5 
26 
O 
5 
15 
10 
1 1 
O 
65 
8 
O 
64 
30 
63 
30 
10 
7 
7 
11 
6 
10 
47 
10 
29 
68 
7 7 
63 
22 
64 
43 
64 
3 
8 
5 
5 
14 
40 
14 
15 
13 
52 
8 
T 1 
66 
59 
66 
23 
65 
45 
7 
4 
4 
17 
26 
16 
57 
16 
29 
13 
2 2 
69 
5 
68 
31 
67 
35 
2 
1 
1 
21 
25 
20 
52 
20 
18 
5 
ir 
72 
20 
71 
50 
71 
20 
11 
5 
5 
24 
9 
23 
32 
22 
55 
17 
4 4 
74 
44 
74 
18 
73 
51 
5 
2 
2 
27 
37 
26 
56 
26 
15 
4 
I r 
75 
42 
75 
18 
74 
53 
3 
1 
1 
32 
6 
31 
22 
30 
37 
19 
5 5 
76 
34 
76 
11 
75 
47 
22 
7 
7 
33 
11 
32 
25 
31 
40 
82 
23 23 
77 
41 
77 
19 
76 
57 
17 
5 
5 
34 
54 
34 
7 
33 
20 
7 
2 2 
78 
0 
77 
40 
77 
18 
4 
1 
1 
38 
7 
37 
19 
36 
30 
10 
3 3 
78 
54 
78 
35 
78 
15 
13 
3 
3 
39 
35 
38 
44 
37 
55 
23 
7 7 
79 
11 
78 
52 
78 
32 
31 
7 
7 
39 
56 
39 
10 
38 
17 
3 
ir 
80 
57 
80 
41 
80 
25 
6 
1 
1 
44 
27 
43 
37 
42 
46 
122’ 
43 43 
82 
5 
81 
51 
81 
37 
20 
3 
3 
45 
45 
44 
54 
44 
3 
17 
6 6 
82 
7 
81 
53 
81 
38 
7 
1 
1 
46 
18 
45 
28 
44 
37 
11 
4 4 
82 
44 
82 
31 
82 
18 
13 
1 
1 
51 
28 
50 
39 
49 
49 
35 
13 Ts 
83 
11 
82 
39 
82 
47 
14 
1 
1 
51 
54 
51 
5 
50 
15 
8 
3 3 
83 
24 
83 
12 
82 
59 
16 
1 
1 
52 
36 
31 
47 
50 
58 
21 
8 8 
83 
44 
83 
33 
83 
19 
20 
1 
1 
63 
35 
52 
47 
51 
57 
76 
^ 29 
83 
46 
83 
35 
83 
24 
1 
0 
0 
57 
30 
36 
44 
55 
57 
19 
8 8 
85 
53 
85 
30 
83 
42 
11 
T 
I 
64 
27 
63 
48 
63 
7 
116 49 49 
86 
1 
85 
34 
85 
47 
