Packing of the Ice. 115 



The Aurora Borealis was visible at observation-hour on 24 

 nights ; and Lunar Halos were visible at the same hour on 6 

 nights. The Zodiacal Light was unusually bright at the evening 

 observations, but the morning observations did not show any such 

 increased brightness. 



St. Martin, Isle Je"sus, 3d April, 1858. 



ARTICLE XIII.— On the Packing of the Ice in the River St. 

 Lawrence. — By Sir W. E. Logan. 



(From the Proceedings of the Geological Society of London, for June 

 15, 1842 ; vol. iii., p. f66.) 



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 throvra 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 



