A popular treatise on gems, in reference to their scientific value; a guide for the teacher of natural sciences, the jeweller, and amateur: together with a description of the elements of mineralogy, and all ornamental and architectural materials .. (1859)
Feuchtwanger, Lewis. [from old catalog] · New York, D. Appleton & company · leaf 51
ges of the rhombohedron, as in figure42, the scalenohedron is constructed. Hence it is desig-nated by mR, the n being written on the right hand, likean algebraic exponent: and the dihexagonal prism is inlike manner designated by ooR. 44 A PEACTICAL TREATISE OX GEMS. The combinations of rhombohediic… … Fig. 43, Fig. 44. with the sign ooR, — iR, the lower half being the sameform with the upper, but turned round 180°. In figure44, the rhombohedron mR has its polar edges replaced by
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