OUTLINES OF MINERALOGY. Nor to the surface of enlivened earth, Hence Labour draws his tools; hence burnished War HYMN to the SUN. On the first view of the science of mineralogy, it would seem one of the least attractive; but a closer inspection soon discovers it to be of the highest importance, and that from the fairest diamond or most brilliant ruby, down to the commonest sand or gravel of our footpaths, all merit our closest attention. Some conduce largely to our domestic comforts and commercial advantages in the form of fuel, as the various kinds of coal; others are useful in medicine, as sulphur, arsenic, mercury, &c. Of the metals, man has availed himself, and with these, aided by the assistance of fire, is enabled to reduce the other parts of the creation to his use and purposes. The name of mineral, in the strict sense of the word, denotes only such substances as are found in mines; but the term is generally applied, in a more extended sense, to characterize that class of inorganic and inanimate bodies which form the solid mass, or rather the external covering, of the globe we inhabit, -so far at least as the labour of man has hitherto penetrated. Minerals, like organized bodies, have a certain origin, progressively increase, and are subject to dissolution or decomposition of parts. But they arise merely by an accumulation of homogeneous or similar particles from without; either by substances combining in consequence of their attractive power, which is called cohesion; or by the solid particles being separated from the fluid ones, when the former attract each other, according to certain laws, constituting together a solid body; and this is termed crystallization, a form of which only certain minerals are susceptible. Mineralogy is that department of the science of nature which makes us acquainted with the characters of minerals. It teaches the art of distinguishing them by accurate and well defined characters; the mode of describing them with so much precision as is sufficient to recognize them with facility whenever they occur, and the art of arranging or classing them in a certain order or system. The characters of minerals in their most striking properties may be thus illustrated. (1.) Fusibility means the power of being melted. The most ready way to ascertain the fusibility of a mineral substance, is, by exposing a small particle of it to the flame of a candle or lamp concentrated by the instrument called a blow-pipe; and, if the heat thus excited is sufficient to liquefy the mineral, it is said to be fused. (2.) The hardness of minerals is ascertained either by a comparison with each other, or by their power of scratching, glass, or the effect of the file upon them: those which resist the file being the hardest. (3.) The phosphorescence of minerals means the faint light which they emit, either by exposure to simple heat, or in consequence of friction. (4.) The electricity of a mineral is that property which, being excited either by simple heat or by friction, shows itself in the attraction or repulsion of other substances with which the mineral is brought nearly in contact. (5.) By the specific gravity of a mineral, is understood the amount of its weight, when compared with the weight of a quantity of water of the same bulk with itself. (6.) The crystalline forms under which minerals occur are various, and may be considered as one of their most important characters, being, with some few exceptions, resolved into six principal forms. Mineralogy is chiefly employed in arranging similar bodies under the same, and dissimilar bodies under different denominations, and it judges of them by external appearances or internal compositions. (1.) External characters are discovered by observing the figure, colour, texture, fracture, or other properties which the different bodies present to our senses, without undergoing any material alteration. (2.) Internal constitution. This knowledge is acquired chiefly by regarding the changes produced in them by the chemical actions of other bodies. Mineralogy, like almost every other science cultivated in modern times, while its boundaries have been extended, and its principles greatly improved, has been rendered more subservient than formerly to various important purposes of economy and art. Instead of being considered, as it once was, a low and trifling object of study, it has lately begun to be d viewed as dignified in its nature, and most interesting in its relations. It is now regarded as a valuable and indeed necessary handmaid to medicine, agriculture, and a large portion of the manufactures, which supply the conveniences, comforts, or luxuries, of human life. Mineralogy has, therefore, within a few years past, been cultivated with great diligence and success by almost all the nations in Europe, especially in Germany and Sweden, where splendid mineral riches particularly invited inquiry and application. Societies have been formed for extending and improving the science; travellers have explored foreign countries for the same purpose; distinguished eminence in this branch of knowledge has been rewarded by public esteem, and by civil honours; and the most effectual methods used to direct general attention to the subject. In describing the present state of mineralogical science, it may be observed, in the words of Mr. Kirwan, that within a few years precise lines of information have been traced, even in the minuter subdivisions of the science; the gross indications of the unassisted senses, freed from their attendant fallacies, have been pressed into its service; the more refined chemical tests, still further perfected, have been rendered more conclusive; many new species brought to light; the catalogue of the elementary substances nearly completed; and the great art of analysis, extended far beyond its former limits, now nearly approaches the precision of an algebraic formula.' The introduction of the blow-pipe is an important æra in the history of mineralogy. The great value of this invention, in chemical and mineralogical inquiries, will appear from considering that the most intense degree of heat may be obtained by it, with the utmost conveniency, in a few minutes, which can scarcely be obtained by means of a crucible in many hours. Analytical Mineralogy, or the analysis of minerals, is a branch of philosophical chemistry. It teaches the art of examining minerals, not by the help of external characters, but chiefly by chemical agencies. Its views are directed to the developement of the constituent parts of minerals, the order in which they are present, their relative quantities, and the best modes of separating them. Mineral waters are found in those places where there is an abundance of iron, copper, sulphur, and pit-coal. Hence their taste and effects are different, in proportion as they are more or less impregnated with the above principles. They are also subject to other impregnations, and from their salubrious effects in some diseases, when containing different salts, iron, and sulphur, many of these waters have been successfully employed in medicine, and have been termed medicinal. Of the origin of minerals, it is not within the limits of this Introduction to state all the various opinions; nor would it be of much use. For the sake of poetical illustration on a subject not naturally susceptible of this embellishment, it may suffice to observe, that some philosophers have attributed the formation of minerals to the action of the sun without; some, to the influence of the central fire within; and some think that cold is the productive cause, by uniting, condensing, and congealing certain juices of the earth. To the first two opinions Dr. Yalden alludes in the following lines: |