﻿Geological Map, District about Montreal. 251 



passing across the St. Lawrence Valley by any of the 

 other usual lines of travel. 



On 'the line of the Canadian Pacific Eailway between 

 Montreal and Ottawa the Potsdam sandstone is first 

 found at Ste. Scholastique, and on the line of this railway 

 running from Montreal to Toronto it is met at He Perrot, 

 which consists wholly of this formation. 



The Utica fringes either shore of the St. Lawrence 

 from Laprairie to Vercheres, whence, after forming the 

 western portion of He Bouchard, it passes beyond the 

 north shore and along the course of the Canadian Pacific 

 Eailway towards Quebec. The Eichelieu Eiver flows 

 through strata of the LTtica horizon from Lake Champlain 

 to Chambly, and thence to its mouth through the Hudson 

 Eiver formation, which, from He Bouchard northwards, 

 appears on both sides of the St. Lawrence. 



Passing southward, the Grand Trunk Eailway lies 

 wholly on the Utica formation from the Victoria Bridge 

 to St. Johns, and thence to Eouse's Point, while towards 

 the east the Hudson Eiver, which is met a short distance 

 east of St. Lambert, gives place to the Trenton formation 

 near the junction with the Drummond County Eailway. 



This, after enclosing a band of Sillery (Cambrian) slates, 

 is succeeded by the lower Cambrian, and this in turn by 

 Huronian a few miles west of Eichmond. 



It has been already stated that the Huronian formation 

 here comprises the ridges known as the Stoke Mountains 

 and the Sutton Mountain Anticlinal. The age of these 

 rocks has been the subject of much geological controversy, 

 and their establishment in the Huronian system is one of 

 the most important changes from the last map of the 

 district, which was issued in 1866. 



Sir William Logan, in the earlier days of the Geological 

 Survey, determined the age of this series to be Silurian, 

 and believed that the strata, now regarded as part of the 



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