220 Canadian Record of Science. 



inferentially, the existence of these primitive forms of life. 

 If I were to conjecture what were the early forms of plant 

 and animal life, I would suppose that, just as in the Palaeo- 

 zoic, the acrogens culminated in gigantic and complex forest 

 trees, so in the Laurentian, the alga?, the lichens, and the 

 mosses grew to dimensions and assumed complexity of struc- 

 ture unexampled in later times, and that, in the sea, the 

 humbler forms of Protozoa and Hydrozoa were the dominant 

 types, but in gigantic and complex forms. The land of this 

 period was probably limited, for the most part, to high lati- 

 tudes, and its aspect, though more rugged and abrupt, and 

 of greater elevation, must have been of that character which 

 we still see in the Laurentian hills. The distribution of this 

 ancient land is indicated by the long lines of old Laurentian 

 rock extending from the Labrador coast and the north shore 

 of the St. Lawrence, and along the eastern slopes of the 

 Appalachians in America, and the like rocks of the He- 

 brides, the Western Highlands, and the Scandinavian 

 mountains. A small but interesting remnant is that in the 

 Malvern Hills, so well described by Holl. It will be well to 

 note here and to fix on our minds, that these ancient ridges 

 of Eastern America and Western Europe have been greatly 

 denuded and wasted since Laurentian times, and that it is 

 along their eastern sides that the greatest sedimentary 

 accumulations have been deposited. 



From this time dates the introduction of that dominance 

 of existing causes which forms the basis of uniformitarian- 

 ism in geology, and which had to go on with various and 

 great modifications of detail, through the successive stages 

 of the geological history, till the land and water of the 

 northern hemisphere attained to their present complex 

 structure. 



So soon as we have a circumpolar belt or patches of 

 Eozoic l land and ridges running southward from it, we 

 enter on new and more complicated methods of growth of 

 the continents and seas. Portions of the oldest crys- 

 talline rocks, raised out of the protecting water, were now 

 eroded by atmospheric agents, and especially by the car- 



1 Or Archaean, or pre-Cambrian, if these terms are preferred. 



