Page:Transactions of the Geological Society, 1st series, vol. 4.djvu/254

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Measurements.
Substances Primitive Crystal. Reference to Plate 12 According to Haüy According to Bournon By the
Reflecting Goniometer
Cyanite An oblique prism of which the plane P is very nearly a rhomb Fig. 7. M on T 106° 6′ 106° 15′
Haüy
M or T on the adjacent plane, over the edge A 73° 45′
Corundum A slightly acute rhomboid. Fig. 3. P on P 86° 38′ 86° 86° 4′
Haüy & Bournon
P on P' 93° 32′ 94° 93° 56′
Sulphate of Strontian A right prism with rhombic bases. Fig. 2. M on M 104° 48′ 104°
Haüy
M on the adjacent plane, over the edge A 75° 12′ 76°
Carbonate of Lead An octoheron, of which the common base of the pyramid is rectangular Fig. 2. M on the opposed plane over the apex 70° 30′ 71° 40′
Haüy
M on M 108° 20′
P on its opposed plane over the apex 62° 56′ 62° 42′
P on P 117° 18′
A rectangular tetrahedral prism with square bases. Bournon.
Sulphate of Lead A rectangular octohedron. Haüy. Fig.2 P' on P'
P on P
72° 28′
109° 18′
A right tetrahedral rhomboidal prism with rhombic bases. Bournon. Fig. 11. P on P 101° 30′
P on the adjacent plane over the edge a 78° 30′
A right prism with rhombic bases. W.P. Fig. 13. P' on P' 76° 18′
P on the adjacent plane over the edge a 103° 42′

Oxide of Tine


Pl. 12. Fig. 1.


The crystals of this substance admit of cleavage parallel with all the sides of the common prism, and of its diagonals, as well as the faces of the primitive octohedron, which is obtuse. The first is