56 CHEMISTRY OF THE ROCKS. 



on the confines of the enormously extended sphere of vapors, 

 there was found a current sufficiently cool to condense a portion 

 of it. If the vapor of silicon follows the general rule, that the 

 density of gases is in proportion to their atomic weights, then it 

 was but a fraction heavier than oxygen, and therefore not far be- 

 low it in the atmospheric strata. The unceasing commotion of 

 the elements would soon have brought this first cloud-mist of 

 silicon into contact with oxygen, to which it has a strong affinity 

 under high heat. Oxidized, and in molten drops of silica, or 

 crystals of quartz, this new-formed material commenced its de- 

 scent toward the center of gravity the first creation from the 

 primordial elements. As it fell into the more heated regions 

 below, it was probably soon evaporated, and the vapor rising car- 

 ried up with it the heat taken up in the evaporation. It was 

 again condensed, its heat given up, and it descended for another 

 charge of the internal fires. This in all probability is the epit- 

 ome of the process of world-cooling. 



At last the showers of melted silex reached the liquid surface 

 of the nucleus which the force of gravity and compression must 

 have formed, at an early period of the nebulous globe, of less or 

 greater extent about its center. From this period the increasing 

 torrents of silica, intermingled with the silicates which were 

 forming at the same time, poured down through the heavy 

 vapors, arid filled up the furlongs-deep of granite ocean. On 

 this vast deposit, and at about this stage of the gradual cooling 

 of the earth, began, we must suppose, the first hardening and 

 crusting over of the surface, since at this point, near the close of 

 the granite age, first commences the division of the earth's crust 

 into varieties and layers more or less distinct, as also the upbear- 

 ing of the heavy metals which, without this surface-hardening, 

 could never have floated on any molten sea of minerals. The 

 slow cooling of the granite masses beneath this crust and under 

 the enormous atmospheric or other superincumbent pressure, con- 

 formed them to all the acknowledged conditions of the formation 

 of the igneous rocks. 



There is found in the different beds of the'granitic rocks every 

 proportion of the admixture of silica with the silicates of alum- 



