NOME XXIX. GYPSUM, WITH SILEX. [DAVITE, from Davy, 1810.] To this division belongs the noted marble of Vulpino, analysed by Fleurieu de Bellevue*. It is of an uniform whitish grey, sometimes veined with a bluish grey. It forms no effervescence in the nitrous acid, though it has the exterior aspect of a saline marble. When the powder is thrown on burning coals, it yields a slight but easily perceivable phosphoric light. Its specific weight amounts to about 200 French pounds for each cubic foot. It is quarried at Vulpino, 15 leagues from Milan, and is employed with success in that city in making tables, columns, vases, or other works of that kind. Before the analysis it was regarded as a marble. Marble of HYPONOME 1. Uniform. HYPONOME II. Veined. * Brard, ii. 474. Patrin, iii. 222. observations. there are many rocks which, though sometimes composed of not unusual modes, are of so singular a structure, that they deserve to be ranked in a separate Domain; more especially as the greater part are of distinguished dignity and beauty. Others are entitled to this distinction from their gem mose nature, being inlaid, so to speak, with precious substances; such as opaline felspar, lazulite, chrysolite, and topaz. Those rocks may also be regarded as anomalous which are of very rare occurrence, and form, as it were, another class of anomalies from the usual laws and order of nature. Among the latter may be mentioned the hills of rock salt which occur in Spain and Africa; and the hills of iron, intermixed with quartz, to be found in Sweden and Lapland. The few rocks in which barytes is incorporated may also be annexed to this Domain, with Bituminous and Sulphuric Rocks, which are far from common. The mineral kingdom, as already mentioned, is here regarded as divided into only three provinces, Petralogy, Lithology, and Metallogy: the class of Salts and Combustibles being divided between the two former provinces. In fact, the term rock salt indicates the province of the only salt which can properly and strictly be regarded as a mineral; the others being found in Salts and Combustibles. Coal. waters, or deposited by them, or appearing as mere efflorescences, or at the most in a gemmose form. And as the important and interesting study of Crystallography, or Chrystallogy, originated from the observation of the salts, they may be considered as belonging to that department of Lithology. But the Combustibles stand in a different predicament, for coal is, in many countries, a very common and abundant substance; is found in vast beds, like many other rocks; and may be said to constitute entire hills, as that of St. Gilles, near Liege. In this new point of view, therefore, coal has been ranked among the rocks; and that division also includes the bituminous substances, which ouse from them, or may be found in their recesses; while amber and mellilite remain almost alone for the minute investigations of the gemmologist. In passing to the sulphuric substances it must be observed, that a most common Pyrites. and general appearance of sulphur, in pyrites, is so interwoven with most of the rocks, that it forms an important feature in petralogy. From the Alpine granites to the lowest beds of coal, infinite are the rocks which contain pyrites. Henkel has written a large and learned work on pyrites; and a complete investigation of them by the gigantic powers of modern chemistry, might perhaps decide the question so long agitated, whether the rocky shell of this planet have been consolidated and expanded by internal heat, or merely deposited by water. To conceive however that the matter of this globe is wholly inert, seems to be contrary to all the other laws of nature, which abounds with various and prodigious kinds of motion and animation ; and appears to be positively contradicted by the vast force and extent of earthquakes, not to mention inferior pheno mena. However this be, pyrites form an important consideration in the knowledge of rocks. Even native sulphur may be said to constitute rocks at Solfaterra, and in Guadaloupe, and at St. Vincent's, not to men |