304 THE REVOLUTIONS OF THE CKUST OF THE EARTH. 



According to one view, the sedimentary rocks of this first phase of 

 the activity of the waters could be no other than the granites, the 

 syenites, the serpentines, the porphyries, and other rocks reputed primi- 

 tive or of plutouiau nature. We suppose that they remained in a pasty 

 condition as long as they were buried in the earth at a sufficient depth to 

 be influenced by a temperature which maintained them in their primitive 

 state ; but they were hardened by losing the temperature and the water 

 necessary to the solution of their siliceous cement, when by some pressure 

 they were brought to the surface of the globe. This plasticity without 

 incandescence explains clearly why there are no traces of metamor- 

 phism to be found in the rocks injected by granite veins, which would 

 be the case if the rock had been liquid and incandescent. Other facts 

 equally attest the aqueous origin of several granitic rocks. 



Certain quartz, particularly the amethyst, lose their color so easily 

 under the influence of heat, that we are led to the admission of the 

 organic origin of color, which is irreconcilable with the hypothesis 

 of the formation of quartz by dry means. M. Delesse has extended this 

 theory of formation to all the granites. He says, "■ The existence in the 

 granitic rocks of volatile organic material is alone sufficient to prove 

 that they have not been submitted to very great heat ; that they 

 have not an igneous origin." His opinion has been confirmed by the 

 investigations of M. Eose, which show that silica is found in two con- 

 ditions : First, in the amorphous state, which could be produced by 

 humid means and by dry means, with a density of 2.2 to 2.3; second, 

 in the crystalline state, with a density of 2.6 ; it is the hyalin or the 

 granite quartz which can only be formed by humid means or at least 

 under the influence of water.* 



These observations are of the highest importance, and will probably 

 lead to an approximate solution of the question of the true origin of 

 granitic rocks. At present the controversy in regard to this subject is 

 not ended — quite the contrary. 



In proportion as the influence of the sun upon the atmosphere became 

 more apparent, the irregular action of the winds and oceanic currents 

 must have given place, more and more, to a regular iBclination of the 

 fluids of the poles toward the equator, and vice versa. This regularity 

 in the movements of the fluids was greatly affected by the incessant 

 rising of the crust, which, in producing islands of variable extent, local- 

 ized the denuding action of the current upon certain points, which, by 

 their configuration, rendered the velocity of the waters greater. The 

 materials carried away by the currents were dropped as soon as the mo- 

 tion of the waters ceased sufficiently, and formed deposits more or less 

 homogeneous, according to the rapidity of the sedimentation. 



After the emersion of islands and continents, the atmosphere contin- 

 ued the disaggregation of the eruptive and sedimentary rocks, through 

 the influence of humidity, heat, and cold, by electricity and its chemical 



* Favre, Recherches geologiques, t. iii, p. 307. 



