14 REPORT— 1886. 



Let us suppose, then, the floor of old ocean covered with a flat pave- 

 ment of gneiss, or of that material which is now gneiss, the next question 

 is how and when did this original bed become converted into sea and 

 land. Here we have some things certain, others most debatable. That 

 the cooling mass, especially if it was sending out volumes of softened 

 rocky ijaaterial, either in the exoplutonic or in the crenitic way, and piling 

 this on the surface, must soon become too small for its shell, is apparent ; 

 but when and where would the collapse, crushing, and wrinkling inevit- 

 able from this cause begin ? Where they did begin is indicated by the 

 lines of mountain-chains which traverse the Laurentian districts ; but the 

 reason why is less apparent. The more or less unequal cooling, harden- 

 ing and conductive power of the outer crust we may readily assume. 

 The driftage unequally of water-borne detritus to the south-west by the 

 bottom currents of the sea is another cause, and, as we shall soon see, most 

 efiective. Still another is the greater cooling and hardening of the crust 

 in the polar regions, and the tendency to collapse of the equatorial pro- 

 tuberance from the slackening of the earth's rotation. Besides these the 

 internal tides of the earth's substance at the times of solstice would exert 

 an oblique pulling force on the crust, which might tend to crack it along 

 diagonal lines. From whichever of these causes or the combination of the 

 whole, we know that within the Laurentian time folded portions of the 

 earth's crust began to rise above the general surface in broad belts running 

 from N.E. to S.W., and from N.W. to S,E., where the older mountains 

 of Eastern America and Western Europe now stand, and that the subsi- 

 dence of the oceanic areas allowed by this crumpling of the crust permitted 

 other areas on both sides of what is now the Atlantic to form limited 

 tablelands.' This was the beginning of a process repeated again and again 

 in subsequent times, and which began in the Middle Laurentian, when for 

 the first time we find beds of quartzite, limestone, and iron ore, and 

 graphitic beds, indicating that there was already land and water, and 

 that the sea, and perhaps the land, swarmed with animal and plant life 

 of forms unknown to us for the most part now. Independently of the 

 questions as to the animal nature of Eozoon, I hold thau we know, as 

 certainly as we can know anything 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 

 Pal03ozoic the acrogens culminated in gigantic and complex forest trees, 

 so in the Laurentian the algee, the lichens, and the iiiosses grew to 

 dimensions and assumed complexity of structure 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 moat part, to high latitudes, 



' Daubr^e's curious experiments on the contraction of caoutchouc balloons, partially 

 harujned by coating with varnish, shows how small inequalities of the crust, from 

 whatever cause arising, might affect the formation of wrinkles, and also that trans- 

 verse as well as longitudinal wrinkling might occur. 



