A popular guide to minerals : with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy . place of the original octahedron. The axes of the octahedron whichterminated in its solid angles, in the tetrahedrons meet the middleof the opposite edges. Again take the Tetragonal-trisoctahedron (Fig. 16) and re-move the alternate groups of unshaded and shaded faces and thetwo respectively right and left (positive and negative) hemihedralforms are produced, shown by Figs. 17 and 18, sometimes calledtris-dodecahedrons, in which the axe
A popular guide to minerals : with chapters on the Bement Collection of minerals in the American Museum of Natural History, and the development of mineralogy . place of the original octahedron. The axes of the octahedron whichterminated in its solid angles, in the tetrahedrons meet the middleof the opposite edges. Again take the Tetragonal-trisoctahedron (Fig. 16) and re-move the alternate groups of unshaded and shaded faces and thetwo respectively right and left (positive and negative) hemihedralforms are produced, shown by Figs. 17 and 18, sometimes calledtris-dodecahedrons, in which the axes of the full form also meet thecenters of the straight edges. These tris-dodecahedrons are ob-
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectmineral, bookyear1912
