Discoveries and inventions of the nineteenth century (1905)
Routledge, Robert · London : G. Routledge and Sons · leaf 450
n Fig. 204 a perfect rhombohedron, such as that shown inFig. 206, is readily obtained by cleavage; and then we have a solid havingsix lozenge-shaped sides, each lozenge or side having two obtuse angles of101° 55, and two acute angles of 78° 5. Of the eight solid corners, suchas A B c, &c., six… … Fig. 204. angles to the other: the diagonal so drawn forms the optic axis of thecrystal, and a plane passing through the optic axis, A B, Fig. 205, andthrough the bisectors of the angles, E A D and F B G, marks a certain defi-nite direction in the crystal, to which also belong all planes parallel…
Inventions
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