P aching of the Ice. 121 



jammed together down to the very bottom of the river over such 

 extensive areas as have been mentioned, and there solidified by- 

 severe frosts around the projecting materials that present them- 

 selves to its grasp, the ice must seize a multitude of the loose 

 boulders below ; and not only will these be carried away, occa- 

 sionally to very considerable distances, when it breaks up in the 

 spring, but firmly set in their glacial matrix, they will, when in 

 the course of the movements that occur, such masses as hold 

 them are forced over shallow places, act as gravers to register in 

 parallel grooves on the face of such rocks as they encounter, a 

 memento of their progress as they pass along. 



The boulders in the middle of the river may at once be occa- 

 sionally carried to considerable distances ; but it can scarcely be 

 so with such as are stationed at or near the borders. For though 

 these may become packed and imbedded in marginal ice, and by 

 the force of a general movement or shove, as it is termed by the 

 inhabitants, be driven obliquely up the bank, as soon as this 

 ceases they will there be left ; and as these general movements 

 occur only three or four times during a season, and are never of 

 long continuance, and even where the marginal ice is driven up 

 the bank the friction it suffers soon causes succeeding portions to 

 pile over one another, it is evident the boulders would not be 

 carried by it to any very great distance. When a break-up 

 occurs in the spring, it is the great body of ice in the middle of 

 the river that is carried away, which, separating from the ground- 

 ed portion on the margin, leaves this to be melted down by the 

 increasing temperature of the season. The movements of suc- 

 ceeding winteis may push marginal boulders farther and farther 

 on, but .they must at the same time have a tendency to carry all 

 within a certain range gradually nearer to the bank, and at last 

 place them in a position at the very limit of their influence. And 

 it is certainly the case, that in the neighbourhood of Montreal 

 there are in many places along the borders of the river collections 

 of boulders sufficiently great to induce the supposition that their 

 presence" may be accounted for in this manner. 



It is not however only on the immediate banks of the St. Law- 

 rence that boulders abound. They are more or less spread over 

 the whole island of Montreal, and over the plains on the opposte 

 side of the river. I do not pretend to have ascertained their 

 distribution with the precision necessary to permit the expression 

 of an opinion as to the causes which placed them, but I may state 



