10. There are few mines of any considerable depth that would not be flooded with water from internal springs were not means adopted for drawing off this fluid. The steam engines that are employed for this purpose in some of the Cornish mines are so powerful as to discharge incessantly, both by night and day, a quantity of water, equal to at least 1000 gallons, or near twenty hogsheads, every minute.
SYSTEMATIC ARRANGEMENT OF MINERALS.
11. To a superficial observer, perhaps nothing would appear more easy than to describe a mineral. This, however, is by no means the case. The same general appearance sometimes prevails in substances that are very different from each other; and the same stone, in its different states, is often extremely varied in its appearance. To these difficulties it must be added, that the combinations of mineral substances are multiplied to a great extent. A little application, however, particularly if the student be possessed of a collection of arranged and named specimens, which he will have no difficulty in procuring at a reasonable price, will enable him to overcome all the obstacles that otherwise might impede his progress in beginning to acquire a knowledge of this interesting science.[[1]]
12. The most simple and natural division of minerals is into four classes, of, 1. Stones; 2. Salts; 3. Combustibles; and, 4. Metals; and the following table, which has chiefly been arranged from the system of Werner, the well-known German mineralogist, will exhibit a tolerably correct outline of the classification of these substances. To reduce the whole within the compass of a single page, many of the families, however, have necessarily been omitted.
[1]. Such collections are supplied by Mr. Mawe, No. 149, Strand, London. His terms, for collections containing from 100 to 200 specimens, are 5 guineas; from 200 to 300 specimens, 10 guineas; and from 300 to 400 specimens, 15 guineas. For collections containing from 350 to 400 specimens, more select, and comprising a better suite of precious stones, he charges from 20 to 30 guineas; and for larger collections, from 50 to 100 guineas. At the particular request of the author, Mr. Mawe has arranged a few collections of minerals, and numbered them in such manner as to correspond with, and illustrate the present volume.
13.To complete a general view of the different productions of the mineral kingdom, it is requisite to subjoin a tabular arrangement of the various kinds of rocks.
14. For the purpose of ascertaining the names and characters of minerals, attention must be paid to their form, surface, lustre, fracture, or the appearance of their internal surface when broken; structure, transparence, streak, or the mark left when scratched by any hard body; stain, or trace left when rubbed upon paper; cohesion, whether solid, friable, or fluid: hardness, or the resistance which they oppose when scratched; tenacity, or the resistance which they oppose to the stroke of a hammer; flexibility, or their property of bending without breaking; feel, or the sensation communicated by their surfaces when handled; smell, taste, adherence to the tongue, sound, specific gravity, or weight in comparison with that of water; colour and electricity.