THE DAWN OF LIFE 



109 



we cross the Nation River, a stream nearly as large as the 

 Tweed, flowing placidly between wooded banks, which are 

 mirrored in its surface ; but in the distance we can hear the 

 roar of its rapids, dreaded by lumberers in their spring drivings 

 of logs. Arrived at St. Andre, we find a wider valley, the 

 indication of the change to the limestone band, and along this, 

 with the gneiss hills still in view on either hand, and often 

 encroaching on the road, we drive for five miles more to Cote 

 St. Pierre. At this place the lowest depression of the valley is 

 occupied by a little pond, and, hard by, the limestone, pro- 



FIG. 4. Attitude of Limestone at St. Pierre, (a) Gneiss band in the 

 Limestone. (/>) Limestone with Eozoon. (c) Diorite and Gneiss. 



tected by a ridge of gneiss, rises in an abrupt wooded bank by 

 the roadside, and a little farther forms a bare white promontory, 

 projecting into the fields. 



The limestone is here highly inclined and much contorted, 

 and in all the excavations a thickness of about 100 feet of it 

 may be exposed. It is white and crystalline, varying much, 

 however, in coarseness in different bands. It is in some layers 

 pure and white ; in others it is traversed by many grey layers of 

 gneissose and other matter, or by irregular bands and nodules 

 of pyroxene and serpentine, and it contains subordinate beds of 

 dolomite. In one layer only, and this but a few feet thick, 

 does the Eozoon occur in abundance in a perfect state, though 



