What are the chief uses of Silex?
It is the most durable article for the formation of roads; a necessary ingredient in earthenware, porcelain, and cements; and the principal material of glass and vitreous substances. The making of pastes or artificial gems is a branch of the art of glass-making; the basis used is a very hard and pure silex.
Basis, that part of any mixture which is the ground or base; the first principle or element of a substance.
Describe the properties of Lime.
It is of a white color, and possesses a hot, caustic taste. It forms peculiar salts with acids; changes vegetable blues to green; will not fuse; gives out a quantity of caloric when united with water; and absorbs carbonic acid when exposed to air. Lime is very useful in the arts and manufactures, in medicine, &c. The farmers use it as manure to fertilize land.
Caustic, burning, corroding: a term applied to substances which eat away and burn any thing with which they are brought in contact.
In what state is Lime found in nature?
Never native, but combined with other substances;—generally with an acid, and most plentifully with carbonic acid, as in chalk, marble, &c. It is also found in vegetables, and is the basis of animal bones; it likewise occurs in the water of the ocean, and in that of all springs and rivers. The method of procuring lime, from chalk, marble, limestone, oyster-shells, &c., has already been described in a former chapter.
What are the properties of Clay?
Argil, or pure clay, also called alumina, from its being the basis of alum, is soft to the touch, adhesive, and emits a peculiar odor when moistened;—forms a paste with water, and hardens in the fire. Its uses are so various and important, that it would have been almost impossible for man to have attained his present degree of civilization, if it had not been given him by nature in such abundance. Its uses have already been described in the arts of brick-making, pottery, &c. Besides these three principal primitive earths just described, there are seven others, having several properties in common, yet each possessing its different and specific properties, and evidently designed by nature for different purposes of utility.