of elasticity, null in some directions; variation in the mutual inclination of the facets; in the same system, a transition from hemihedral to holohedral forms by sharp grouping in some cases, by striæ like those of pyrites and quartz, of holohedral forms to forms hemitropal in different degrees, and to hemimorphal forms. The complication goes on increasing.
We will end by a last trait of analogy. Just as some animals and plants, when they are by any cause placed in a medium offering the largest sum of propitious conditions, attest the excellence of that medium by a more complete development of the individual and of the number of individuals; as there exists a zoölogical geography and a botanical geography, which distinguishes and enumerates for each species the most favored or most favorable regions—there exists also a mineralogical geography, which fixes the cantonment of particular minerals in certain countries. In the Island of Elba, more than anywhere else, is found oligist iron; in the Hartz and the Ural, ores, and native metals; in India, Brazil, and South Africa, gems and diamonds; in California and Australia, gold; in Canada and Chili, copper; in Siberia, malachite; and in Iceland, Iceland-spar. This study has been elaborated for some substances—tin, for example—in the admirable labors of Élie de Beaumont.
Thus, since we have for minerals an embryology, an anatomy, a nosology, a teratology, and a geography, a vast assemblage of facts many of which are known and more unknown, we may also conclude upon the existence of a mineral biology. When every one of the chapters which it embodies shall have been treated experimentally, we may come into a condition to formulate its laws. The artificial barriers raised by our ignorance between the different branches of knowledge will one after another be leveled. Natural history will become easy, like physics and chemistry, now that physics and chemistry, as Lagrange foresaw, have become easy; or, rather, all the sciences will be consolidated into one science, which will be one because matter, the object of its investigations, is one. Every time the mind of the investigator escapes beyond the work of detail which he daily performs in his laboratory, the contemplation of an ideal far removed, but which he is certain he or those who will follow him will attain, gives him new strength to go back to that daily labor, marks an advance, infinitely little but certain, toward that ideal. A glance over its history shows how mineralogy has grown. It seems as if it were conscious of the end toward which it is tending, of connecting the sciences called natural with the exact sciences. As M. Pilo has happily remarked, mineralogy has traversed the period of magic with the alchemists, the empiric period with the experimenters of the seventeenth century, the naturalist's period with Linnæus, Buffon, and Werner, the geometric period with Haüy, Delafosse, and Bravais, the chemical period with Berzelius, and the physical period with Fresnel,
