Review of A system of mineralogy, by James D. Dana / [Benjamin Silliman].

  • Benjamin Silliman Jr.
Date:
1844
Catalogue details

Licence: Public Domain Mark

Credit: Review of A system of mineralogy, by James D. Dana / [Benjamin Silliman]. Source: Wellcome Collection.

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    Following the order of his crystallographic system, Mr. Dana unfolds this intricate subject by a beautiful series of figures, of which we can notice only the following:— “ Figure 3 represents a crystal of Galena from Rossie. It is a shortened cube ; the lateral faces are very irreg¬ ularly curved, and consist of the primary faces 3. of the cube and the planes truncating the lateral edges. Some of the terminal edges are also truncated. The crystal is surrounded by a low pyramid, consisting of four planes on each of the angles and edges, which, owing to the distortion, do not occur elsewhere on the crystal. The cleavages of the crystal easily explain the relations of the several planes to the primary.” “ Figure 5 of apatite is the same form that is represented in figure 4, but greatly distorted. The planes e', e, between P and the right M, Fig. 4. Fig. 5. are enlarged, while the corresponding planes below are in part oblitera¬ ted. By observing that similar planes are lettered alike, the two figures may be compared throughout.” FifiT 7. Fig. 6. “ Curved Crystals.—Curves in imbedded crystals are of frequent oc¬ currence ; and in implanted crystals they are not very uncommon. The annexed figure of quartz, (fig. 6,) illustrates this kind of distortion ; the
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