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.