THE CANADIAN JOURNAL. 



NEW SERIES. 



No. XY.— MAY, 1858. 



ON THE THEORY OF IGNEOUS ROCKS AND VOLCANOS, 



BY T. STERRY HUNT, 



OV THE GEOLOGICAX STTEVET OF CANADA. 



Bead before the Canadian Institute, \?)th March, 18.58. 



In a note in the American Journal of Science for January, 1858, I 

 have ventured to put forward some speculations upon the chemistry of 

 a cooling globe, such as the igneous theory supposes our earth to have 

 been at an early period. Considering only the crust with which 

 geology makes us acquainted, and the liquid and gaseous elements 

 which now surround it, I have endeavored to show that we may attain 

 to some idea of the chemical conditions of the cooling mass by con- 

 ceiving these materials to again re-act upon each other under the in- 

 fluence of an intense heat. The quartz, which is present in such a 

 great proportion in many rocks, would decompose the carbonates and 

 sulphates, and aided by the presence of water, the chlorids both of 

 the rocky strata and the sea, while the organic matters and the fossil 

 carbon would be burned by the atmospheric oxygen. From these 

 reactions would result a fused mass of silicates of alumina, alkalies, 

 lime, magnesia, iron, etc., while all the carbon, sulphur and chlorine, 

 in the form of acid gases, mixed with watery vapour, azote, and a 

 probable excess of oxygen, would form an exceedingly dense atmos- 

 phere. When the cooling permitted condensation, an acid rain would 

 fall upon the heated crust of the earth, decomposing the silicates, and 

 giving rise to chlorids and sulphates of the various bases, while the 

 separated silica would probably take the form of crystalline quartz. 



In the next stage, the portions of the primitive crust not covered 

 by the ocean, undergo a decomposition under the influence of the hot 



VOL. III. O 



