﻿250 Canadian Record of Science. 



topographical features. This renders it exceedingly in- 

 teresting, as a glance at any familiar locality or line of 

 travel shows at once the geological formations to be seen. 



Thus, in crossing the St. Lawrence Valley from St. 

 Jerome to Montreal by the Canadian Pacific Eailway, and 

 thence to West Brome by the Central Vermont RR., the 

 chief geological formations of the Cambro-Silurian system 

 are found. 



After leaving the Laurentian, about a mile south of the 

 village of St. Jerome, the Potsdam sandstone is crossed 

 for about an equal distance, when the Calciferous is 

 reached. This extends to the Ste. Rose River. The Chazy 

 formation reaches from this river to Outremont, where it 

 it is succeeded by the Trenton, which continues to the 

 St. Lawrence. 



The former of these includes the limestones seen at 

 Sault au Recollect, the latter those of Mile End and the 

 City of Montreal. From the western abutment of A^ictoria 

 bridge the Utica shales pass under the St. Lawrence' 

 River, and extend a few miles east of St. Lambert. Here 

 the Hudson River, or Lorraine, formation is met. This is 

 the highest horizon in the geological column that is repre- 

 sented on this map, with the exception of the limestones 

 of St. Helen's Island and Lake Memphremagog of Lower 

 Helderberg (Silurian) age and the small areas of Devonian, 

 both of which have been previously mentioned. 



The Hudson River shales and sandstones extend to the 

 vicinity of Farnham, whence the remainder of the section 

 to Sweetsburg is occupied by the Trenton and Chazy 

 formations respectively, their approximate point of division 

 being East Farnham. 



From Sweetsburg to West Brome only the Cambrian is 

 found, but from the latter point the Huronian extends to 

 the vicinity of the mountains on the west of Lake 

 Memphremagog. 



These formations, or their equivalents, may be seen in 



