I. 



THEORY OF IGNEOUS ROCKS AND 

 VOLCANOES. 



(1858.) 



The following Essay, read before the Canadian Institute, at Toronto, March 13, 1858, 

 was printed in the Canadian Journal for May of the same year. It may be regarded 

 as a first contribution to the theoretical notions developed in some of the following 

 papers. 



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. Consid- 

 ering 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 conceiving 

 these materials to again react upon each other under the influ- 

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

 a great proportion in many rocks, would decompose the car- 

 bonates and sulphates, and, aided by the presence of water, 

 the chlorides 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 vapor, azote, and 

 a probable excess of oxygen, would form an exceedingly dense 

 atmosphere. When the cooling permitted condensation, an 

 acid rain would fall upon the heated crust of the earth, de- 

 composing the silicates, and giving rise to chlorides and sul- 

 1. A 



