all systems of scientific knowledge will soon be laid in molecular physics.
In the constituents of the solid earth we have forms and conditions of matter of remarkable composition and complexity. The original materials of the ground, of the rocks, and of the mines, are found to be, in every case, fully saturated chemical compounds. Many of them, as the silicates, are adamantine acids neutralized by alkaline bases harder than the flint. They could not be made more stable, inert, and solid. They are materials that have apparently gone through stupendous changes, activities, and combustions, and at last have settled down to a rest that knows no waking. Science has no duty more legitimate or more imperative than to inquire how these rock-masses came to be where they are, and in the condition they are.
In pursuing this inquiry—since we find one of the alternatives to be inadmissible—it is necessary, therefore, to accept the other, namely, that the matter which composes the geological formations preëxisted as simple elements, either in liquid or gaseous form. Oxygen, which makes up fully one-half the weight of the solid parts of the earth, is and always was a gas in its free state. In regard to the remaining elements that enter into their composition, such as silicon, aluminum, calcium, and sodium, they could not all have existed on the earth at the same time as melted liquids; for the same heat which held one in fusion would have evaporated others. Some, therefore, must have been contained in the atmosphere as simple gaseous elements. Inasmuch as granite is the base and substratum of all the other formations, if we show that this must originally have been in a gaseous state, we show that every other material must have been at the same time in like condition.
The granitic rocks are by far the most abundant terrestrial substance that we know of. Geologists assign to them a depth of not less than thirty miles. And still below them there is the same or nearly the same chemical substance in fusion, as the fact and analysis of volcanic products sufficiently prove. The compound which is in excess in all granite rocks is silica, the oxide of the element silicon. The varieties are formed chiefly by small percentages, more or less, of the oxides, alumina, and magnesia. This silica, or quartz, as well as the other components of the igneous rocks, is what has been termed "burnt material." It is the product of a most complete and tremendous conflagration; for the oxidation of silicon is as much and as powerful a combustion as the oxidation or burning of coal. To accomplish this burning, every particle of the silicon must have been brought into contact with oxygen gas. This would have been simply impossible if the mineral element had always been in a melted mass of miles in depth; for this, if for no other reason, that the oxygen could not get at it—certainly not, if it was covered by other solid or liquid substances. Or, if it were conceded that silicon ever formed the sur-
