[37] “Gay Lussac first made the remark, that a crystal of potash alum, transferred to a solution of ammonia alum, continued to increase without its form being modified, and might thus be covered with alternate layers of the two alums, preserving its regularity and proper crystalline figure. M. Beudant afterwards observed that other bodies, such as the sulphates of iron and copper, might present themselves in crystals of the same form and angles, although the form was not a simple one, like that of alum. But M. Mitscherlich first recognised this correspondence in a sufficient number of cases to prove that it was a general consequence of similarity of composition in different bodies.”—Graham’s Elements of Chemistry (1842), p. 136.
The following remarks are from a paper by Dr. Hermann Kopp, On the Atomic Volume and Crystalline Condition of Bodies, &c., published in the Philosophical Magazine for 1841:—“The doctrine of isomorphism shows us that there are many bodies which possess an analogous constitution, and the same crystalline form. Our idea of the volume (or, in other words, of the crystalline form) of these bodies must therefore be the same. From this it follows that their specific weight is connected with mass contained in the same volume. From these considerations the following law may be deduced: The specific weight of isomorphous bodies is proportional to their atomic weight, or isomorphous bodies possess the same atomic volume.”—page 255. A translation appears in the Cavendish Society, from Dr. Otto’s Chemistry, On Isomorphism, which may be advantageously consulted. See also a paper by M. Rose, translated from the Proceedings of the Royal Berlin Academy for the Chemical Gazette, Oct. 1848, entitled, On the Isomeric Conditions of the Peroxide of Tin.
[38] A System of Mineralogy, comprising the most recent discoveries, by James D. Dana, A.M., New York, 1844.
[39] Crystallogeny, or the formation of crystals, is the term employed by Dana, in his admirable work quoted above: whose remarks on Theoretical Crystallogeny, p. 71, are well worthy of all attention.
[40] On the Magnetic Relations of the Positive and Negative Optic Axes of Crystals, by Professor Plücker, of Bonn.—Philosophical Magazine, No. 231 (3rd Series), p. 450. Experimental Researches on Electricity; On the Crystalline Polarity of Bismuth and other bodies, and on its Relation to the Magnetic form of Force: by Michael Faraday, Esq., F.R.S.—Transactions of the Royal Society for 1848.
[41] In the Memoirs of the Geological Survey of the United Kingdom, and of the Museum of Economic Geology, vol. i. 1846, will be found a paper, by the author of this volume, On the Influences of Magnetism on Crystallisation, and other Conditions of Matter, in which the subject is examined with much care. See also Magnétisme polaire d’une montagne de Chlorite schisteuse et de Serpentine: Annales de Chimie, vol. xxv. p. 327; Influence du Magnétisme sur les actions chimiques, by l’Abbé Rendus; and also a notice of the experiments of Ritter and Hansteen, “Analysées par M. Œrsted;” also Effets du Magnétisme terrestre sur la précipitation de l’Argent, observés par M. Muschman: Annales de Chimie, vol. xxxviii. p. 196–201.
[42] The transparent varieties of sulphate of lime are distinguished by the name Selenite; and the fine massive varieties are called Alabaster. Gypsum forms very extensive beds in secondary countries, and is found in tertiary deposits; occasionally, in primitive rocks; it is also a product of volcanoes. The finest foreign specimens are found in the salt mines of Bex, in Switzerland; at Hall, in the Tyrol; in the sulphur-mines of Sicily; and in the gypsum formation near Ocana, in Spain. In England, the clay of Shotover Hill, near Oxford, yields the largest crystals.—See Dana’s Mineralogy, second edition, p. 241.