422 



PROCEEDINGS, 



ETC. 



POSTPONED PAPERS. 



1 . On the Packing of the Ice in the River St. Lawrence ; the oc- 

 currence of Landslips in the Modern Deposits of its Valley ; and 

 the existence of Marine Shells in tliem and on the Mountain of 

 Montreal. By W. E. Logan, Esq., F.G.S. 



[Read June 15, 1842.] 



The island of Montreal stands at the confluence of the rivers Ot- 

 tawa and St. Lawrence, and is the largest of several islands splitting 

 up these mighty streams, which cannot be said to be thoroughly 

 mingled until they have descended some miles below the whole 

 cluster. The rivers first come in contact in a considerable sheet of 

 water called Lake St. Louis, which separates the upper part of the 

 island of Montreal from the southern main. But though the streams 

 here touch, they do not mingle. The waters of the St. Lawrence, 

 which are beautifully clear and transparent, keep along the southern 

 shore, while those of the Ottawa, of a darker aspect, though by no 

 means turbid, wash the banks of the island ; and the contrast of 

 colour they present strongly marks their line of contact for many 

 miles. 



Lake St. Louis is at the widest part about six miles broad, with 

 a length of twelve miles. It gradually narrows towards the lower 

 end, and the river as it issues from it becoming compressed into the 

 space of half a mile, rushes with great violence down the Rapids of 

 Lachine, and, although the stream is known to be upwards of eight 

 feet deep, it is thrown into huge surges of nearly as many feet high 

 as it passes over its rocky bottom, which at this spot is composed of 

 layers of trap extending into floors that lie in successive steps. 



At the termination of this cascade the river expands to a breadth 

 of four miles, and flows gently on, until it again becomes cramped 

 up by islands and shallows opposite the city of Montreal. From 

 Windmill Point and Point St. Charles above the town, several ledges 

 of rock, composed of trap lying in floors, which in seasons of low 

 water are not much below the surface, shoot out into the stream 

 about 1000 yards ; and similar layers pointing to these come out 



