LIFE IN THE PAST 1 67 



Eozoic time for us to assert with any positivcness that 

 the ancestral habit is responsible for this trait in the 

 descendants. Sure it is that to-day our cells, like their 

 ancestors of old, live in water, and this water is 

 slightly salty — as were probably the Archaean seas. 



The geologist tries as best he may to build up the 

 geography of the earth in the past. He endeavors to 

 judge from the rocks as he now finds them, where the 

 seas, the bays, the dry land, and the mountains of 

 earlier geological times lay. The present aspect of 

 the earth is very recent, and earlier ages must have 

 shown an entirely different distribution of land and 

 water. The North American continent was certainly 

 very much smaller than it is now. The first known 

 lands lay close to the Atlantic seaboard and probably 

 extended out into the water some distance beyond the 

 present shoreline. The stretch of continent was nar- 

 row, and grew narrower as it went southward. In 

 what is now the Canadian district, a considerable 

 expanse probably existed in very early times. Then 

 a great internal sea, shallower than the Atlantic, 

 stretched its unbroken sheet over almost the entire 

 area now occupied by the United States, while only a 

 comparatively small hump of earth, ending in a nar- 

 rower strip, lay where the great Western plateau now 

 rears its enormous bulk. 



A large portion of the history of the North Amer- 



