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 65
n a commoncentre, between which thecrystal is so placed that itsfaces coincide with the edgesof the rulers, and the angle isthen measured on a graduatedarc. This instrument is suffi-ciently accurate for many pur-poses and for large crystals;but for precise determinationis far inferior to the… … Fig. 6i). FOEM OF MINERALS. 59 be attained, and the measurement depended on to onem.imite (1). The reflecting goniometer is represented in fig. 69. Itconsists essentially of a graduated circle mm, divided on itsedge into twice 180°, or more often into half degrees, theminutes being read off by the…
Precious stones · Building stones · Mineralogy
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