216 Canadian Record of Science. 



igneous rocks. 1 (4) Chaotic or Ther mo-chaotic, or the theory 

 of deposit from the turbid waters of a primeval ocean either 

 with or without the aid of heat. In one form this was the 

 old theory of Werner. 2 (5) Crenitic or Hydro-thermic, which 

 supposes the action of heated waters, penetrating below the 

 crust, to be constantly bringing up to the surface mineral 

 matters in solution and depositing these so as to form fels- 

 pathic and other rocks. 3 



It will be observed, in regard to these theories, that they 

 do not suppose that the old gneiss is an ordinary sediment, 

 but that all regard it as formed in exceptional circumstances, 

 these circumstances being the absence of land and of sub- 

 aerial decay of rock, and the presence wholly or principally 

 of the material of the upper surface of the recently hardened 

 crust. This being granted, the question arises, ought we 

 not to combine these several theories and to believe that the 

 cooling crust has hardened in successive layers from with- 

 out inward ; that at the same time fissures were locally dis- 

 charging igneous matter to the surface; that matter held in 

 suspension in the ocean and matter held in solution by heated 

 waters rising from beneath the outer crust were mingling 

 their materials in the deposits of the primitive ocean ? It 

 would seem that the combination of all these agencies may 

 safely be evoked as causes of the pre- Atlantic deposits. This 

 is the eclectic position which I endeavoured to maintain in 

 my address before the Minneapolis Meeting of the American 

 Association in 1883, and which I still hold to be in every 

 way probable. 



A word here as to metamorphism, a theory which, 

 like many others, has been first run to death and then dis- 

 credited, but which, owing to the moderate degree in which 

 it was originally held by Lyell, is still vai,id. Nothing can 

 be more certain than that the composition of the Lauren- 

 tian gneisses forbids us to suppose that .Jiey can be ordi- 

 nary sediments metamorphosed. They ar<< rocks peculiar 

 in their origin, and not paralleled, unless exceptionally, in 



1 Lyell, Kopp, Reusch, Judd, &c. 



2 Scrope, De LaBeche, Daubr£e. 



3 Hunt, Transactions Royal Society of Canada, 1885. 



