THE LAURENTIAN EOCKS. 15 



It is interesting to notice liere tliat tlie Laurentian 

 rocks thus interpreted show that the oldest known 

 portions of our continents were formed in the waters. 

 They are oceanic sediments deposited perhaps when 

 there was no diy land or very little^ and that little 

 unknown to us except in so far as its debris may have 

 entered into the composition of the Laurentian rocks 

 themselves. Thus the earliest condition of the earth 

 known to the geologist is one in which old ocean 

 was already dominant on its surface ; and any pre- 

 vious condition when the surface was heated, and the 

 water constituted an abyss of vapours enveloping its 

 surface, or any still earlier condition in which the 

 earth was gaseous or vaporous, is a matter of mere 

 inference, not of actual observation. The formless 

 and void chaos is a deduction of chemical and physical 

 principles, not a fact observed by the geologist. Still 

 we know, from the great dykes and masses of igneous 

 or molten rock which traverse the Laurentian beds, 

 that even at that early period there were deep-seated 

 fires beneath the crust; and it is quite possible that 

 volcanic agencies then manifested themselves, not only 

 with quite as great intensity, but also in the same 

 manner, as at subsequent times. It is thus not un- 

 likely that much of the land undergoing waste in 

 the earher Laurentian time was of the same nature 

 with recent volcanic ejections, and that it formed 

 groups of islands in an otherwise boundless ocean. 



However this may be, the distribution and extent 

 of these pre-Laurentian lands is, and probably ever 



