442 Forbes — Chemutry of the Primeval Earth. 



that the attractions of palseontological research have caused it to be 

 of late, in a great measure, shelved by geologists in general. 



It has lately been the fashion, especially amongst many of the 

 younger votaries of the science, to " pooh-pooh " the igneous origin of 

 eruptive rocks in general, and of granite in particular. A careful 

 study of the literature of the subject shows, however, that this 

 secession from opinions, previously all but universally adopted, has 

 originated in the writings of one or two able but one-sided men of 

 science, blindly followed, as is usual in such cases, by adherents who 

 reason not for themselves, or who have either not sufficient leisure 

 or inclination to examine into the true merits of the question. The 

 author fully believes, however, that had anything like a careful 

 study of what has already been published iy'pro et contra) ujDon this 

 subject been made, that not only would an explanation or answer 

 have been discovered to meet any and all of the arguments brought 

 forward in opposition to the igneous origin of such rocks, but that 

 such as are open to conviction would with the author of these 

 remarks have come to the conclusion that nothing has as yet been 

 advanced which can in any way tend to prove the eruptive rocks to 

 have an origin differing from that of those rocks produced by vol- 

 canic action at the present day. 



At present, however, only such arguments as are advanced in Dr. 

 Hunt's lecture can be discussed, and these only in all brevity, since 

 the space already occupied by this communication has extended 

 beyond its proposed limits. 



As evidence against the non-igneous origin of granite. Dr. Hunt 

 asserts " that the composition of the primitive crust would have 

 excluded free silica ;" again, " that this very quartz, which is one of 

 the constituent elements of granite, is only the result of a secondary 

 process ;" and yet again, in the report of his lecture contained in the 

 " Chemical News," vol. xv., p. 317 (revised by himself previous to 

 publication), " that granite is in every case a rock of sedimentary 

 origin, as it includes in its composition quartz which, so far as we 

 know, can only be generated by aqueous agencies, and at compara- 

 tively low temperatures."^ 



In making such statements, it may be asked whether Dr. Hunt is 

 aware of the immense masses of undoubted volcanic rocks scattered 

 all over the surface of the globe which contain abundance of free 

 quartz? Amongst others, the Ponza Islands, for example, under 

 the very shadow of Vesuvius ; the hundreds of miles of volcanic 

 outbursts of quartz trachytes, from the still active volcanoes situated 

 along the range of the Andes, in South America, as well as numerous 

 examples which might be referred to in other parts of the globe, 

 although, unfortunately, not in Canada. Does not Dr. Hunt know 

 that the admirable memoir of Sorby, contained in the Quart. Jouru. 



1 If we, witli Dr. Hunt, believe ttat the temperature increases in proportion to 

 the pressure, then, as Sorby has shown that the quartz of the granite of Aberdeen 

 has solidified at a pressure equal to a column of seventy-eight thousand feet of rock, 

 this alone would be quite sufficient to refute the statement of comparatively low 

 temperatures. 



