THE CHEMISTRY OF THE ROCKS. 695 



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 stupen- 

 dous changes, activities, and combustions, and at last have settled 

 down to a rest that knows no waking. Science has no duty more le- 

 gitimate 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, name- 

 ly, that the matter which composes the geological formations preex- 

 isted 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 re- 

 maining 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 ele- 

 ments. 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 sub- 

 stance 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 tremen- 

 dous conflagration ; for the oxidation of silicon is as much and as 

 powerful a combustion as the oxidation or burning of coal. To accom- 

 plish this burning, every particle of the silicon must have been brought 

 into contact with oxygen gas. This would have been simply impos- 

 sible 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- 



