Of the Vicinity of Montreal. 403 



The thickness of these beds is at least 100 feet, of wbich the 

 lower or boulder clay constitutes the greater part, but the sand often 

 attains the thickness of 10 feet, and the fine clay that of 20 feet. 



The boulders are not confined to the boulder clay, properly so- 

 called. The stratified clays and sands often contain large 

 rounded stones, partly of the mountain trap and partly of the 

 older metamorpbic rocks of the Laurentian formation, lying to 

 the northward of the St. Lawrence valley. Dr. Bigsby long ago 

 remarked that the boulders derived from the mountain have been 

 drifted principally to the S. AV. ; in which direction they have been 

 traced as far as the South Shore of Lake Ontario, 2Y0 miles dis- 

 tant from their original position. On the other hand, the succes' 

 sive terraces are best seen on the North East side of the mountain, 

 which is bai'e and abrupt. 



Wherever I have observed the rock surfaces under the boulder 

 clay, they present the striated and polished appearance usual in 

 such positions. On the North East side of Montreal mountain 

 the directions observed were from S. 70 *-* W. to S. 50 '-' W., 

 corresponding to the direction of the drift mentioned above. 



In some places the surface of the boulder clay has been deeply 

 cut into furrows by the currents which deposited sand and gravel 

 upon it. In like manner the surface of the stratified clay is some- 

 times cut into trenches filled by the overlying sand. On the 

 other hand, in places which have been more sheltered, the boulder 

 clay passes into the finer clay or into gravel, and the latter into 

 sand. It is in these last localities, where evidences of denudation 

 are absent, that marine fossils most abound. 



The City of Montreal is built on the deposits just described. 

 In the upper part of the city, at the base of the mountain, and at 

 the height of about 100 feet above the river, we see in many 

 places a fine yellowish sand, and about the same level, a little 

 further East, at the mile-end quarries, are stratified gravel and 

 sand. Below this sand we find the fine unctuous clay, forming a 

 thick bed in the upper part of the city, and at the brick yard on 

 the St. Lawrence Road, as well as at the village of the Tanneries, 

 Under this is the thick bed of boulder clay and clay gravel seen 

 in_ excavations on Dorchester and Lagauchetiere Streets ; and at 

 the gravel pits on the Lachine Railway. The steep descent at 

 Beaver Hall Hill, at St. Patrick's Hospital, and along the Lachine 

 road is the true margin of the river bottom, and marks the limit 

 of the cut made by the St. Lawrence in these tertiary deposits. 



