peculiar structure and appearance frequently met with unsurpassable difficulties. Even our most modern expedients do not enable us to imitate more than a few well characterized and crystallized minerals regarding shape, luster, and other physical properties. We can build up the carbonates of calcium, iron, and manganese from their elements, but we lack the means to give them the rhombohedral form in which they are naturally found. It was only in the course of the last year that Krontschuff made known the first method of crystallizing silica in the hexagonal form of quartz; and that Fremy and Meunier succeeded in gaining real rubies and spinels by a melting process. It also required long years of incessant experimenting to find out a way of manufacturing the splendid blue coloring matter, ultramarine, as an approximative imitation of lapis lazuli. We should be at a loss, if requested to prepare crystallized manganic binoxide, or calcium triphosphate, or most other crystallized compounds spread throughout the rocky schists of the earth.
Asking for the reason of this insufficiency of our chemical faculties, we find it to be the impossibility of providing, through a sufficient length of time, those conditions of heat, pressure, and other circumstances which prevailed and were of influence when such compounds were separating from molten masses of mineral matter, or from saturated solutions, the composition of which will always remain concealed from us. Organic substances, on the contrary, of the most various kinds, are continually formed and decomposed in the bodies of plants and animals, very readily combining and separating under conditions which exist everywhere, or which may easily be induced. The extraordinary mutability of the compounds of carbon with hydrogen and oxygen is a feature particular to this element, not equaled by those of any other. Their liability to chemical changes enables us voluntarily to build up and to reconstruct carbon compounds occurring in organisms as well as those derived from them.
Alcohol, one of the best-known products of chemical industry, may serve as evidence to what degree of perfection the composition and decomposition of chemical compounds has been brought. As the chief constituent of intoxicating beverages, alcohol, together with carbonic acid, originates by fermentation from sugar; but this is not the only possible way to produce it. The brightness of electric lights, by which public places, roads, stores, etc., of our cities now are illuminated at night, is emitted by an electric current passing between two carbon points. When such a passage of electricity takes place in a glass balloon filled with hydrogen, the electric current causes this gas to unite with carbon, forming acetylene, a gaseous compound, which in contact with more hydrogen readily takes it up, forming a second gaseous compound—
