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“Science has succeeded in classifying the thousands of known crystals in six systems, to each of which belongs a number of forms having some property in common. In order to classify these different crystals, the existence of certain lines within the crystal, called axes, is assumed, around which the form can be symmetrically build up. These axes are assumed to intersect in the center of the crystal, and to pass through from one side to the other.” — Hallock, 1905


crystal, axes, cube, axis




V. I. Hallock I.C.S. Refrence Library (Scranton: International Textbook Company, 1905)


TIFF (full resolution)

2400×2117, 1.2 MiB

Large GIF

1024×903, 162.4 KiB

Medium GIF

640×564, 81.1 KiB

Small GIF

320×282, 28.2 KiB