THE LAUEENTIAN EOCKS. 21 



enormous pines^ which constituted the original forest. 

 Half way we cross the Nation Eiver, a stream nearly 

 as large as the Tweedy flowing placidly between 

 wooded banksj 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^ 

 and which we were told swallowed up five poor fellows 

 only a few months ago. 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^ protected by a ridge of gneiss, rises in an 

 abrupt wooded bank by the roadside, and a little 

 further forms a bare white promontory, projecting into 

 the fields. Here was Mr. Lowe's original excavation, 

 whence some of the greater blocks containing Eozoon 

 were taken, and a larger opening made by an enter- 

 prising American on a vein of fibrous serpentine, 

 yielding '^rock cotton," for packing steam pistons 

 and similar purposes. (Figs. 5 and 6.) 



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 gray layers of 

 gneissose and other matter, or by irregular bands and 



