526 



ON THE GEOLOGY OF CAPE BEETON ISLAND. 



absence in Cape Breton of the fossiliferous marine clay characterizing 

 the Post-Pliocene clays of the Lower St. Lawrence, and this may 

 he due to rapid elevation of the land. At present it is thought by 

 some that a slow subsidence is taking place. 



The Carboniferous measures of the Sydney district have suffered 

 greatly by the action of the ocean, which is rapidly wearing them 

 away. At some points, according to Mr. E. Brown, the shore 

 recedes at an average rate of five inches per annum. This waste of 

 the softer measures has furnished material for the sand-beaches 

 which are numerous around the Bras d'Or Lake and along the 

 south coast of the island. The older rocks are often rounded, but 

 seldom show strise. Around Sydney Harbour and to the east and 

 south of Sydney the striae are observed chiefly on the Millstone Grit, 

 and vary between S. 45° W. and S. 78° W. magnetic. Similar 

 courses are met with at East Bay, Gabarus Bay, Pramboise, and other 

 points on the south shore. 



It is perhaps probable that the courses of the compact ridges of 

 the Pre-Cambrian strata have determined much of the denudation, 

 and that the Bras d'Or Lake and the principal river-valleys owe 

 their form to the cutting-out of the softer shales and sandstones, 

 which are now frequently presented as fringing the harder and 

 older measures. 



Some of the lakes present interesting marks of the action of ice. 

 The winter's ice, when melted around the shores of the lakes and 

 moved by ' the wind, frequently drives large boulders for yards 

 before it ; these leave long furrows in the mud, and remain, with 

 a mass of small stones and earth, in front of them. In other cases, 

 lakes are in this manner surrounded by dyke-like walls of stones 

 and earth. 



