70 / 



whilst at Chomonix the ice near the shore of the mer-de-glace was found 



to move as follows, from June 29th to June 8th of the following year : 



From June 29 to Sept. 28 132 feet. 



" Sept. 28 " Dec. 28 70 " 



" Dec. 12 " Feb. 17 76 " 



" Feb. 17 " April 4 66" 



" April 4 " June 8 88 " 



Total (in less than one year) 432 feet 



This would average over five hundred feet or about one-tenth of a mile 

 in twelve months. The rapidity in the motion of a glacier, of course, 

 depends upon the nature of the obstacles to be surmounted, as well as 

 to a great extent upon the time or month of the year, different portions 

 of the same glacier moving at different rates. A glacier which decends 

 into a valley below, or discharges itself into a sea or arm of an ocean, 

 does not necessarily lose any of its length, for whilst its snout is being 

 melted and carried away to warmer portions, the head or initial point is 

 ever receiving additional snow and ice to supply it constantly, and only 

 a subsidence of the continent could produce a change in the climate of 

 such an ice bound district. 



We have no data existing here or traces left by means of which we 

 can calculate the rate of motion of the glaciers about Ottawa during the 

 great ice age, suffice it to say that as in the case of modern glaciers their 

 rate of travelling varied at different times. Then as to the thickness of 

 the great ice-mass which then invaded this district, that is a problem 

 which to a great extent, has yet to be solved with us, nevertheless, let 

 us examine the data at our disposal in reference to this interesting 

 phenomenon. Taking the Ottawa Valley, in and around the city, as a 

 typical example of a valley of erosion with subordinate branches, we 

 see that facing the river and the north, there occurs a series of high 

 " bluff's " or cliff's where the strata are clearly seen along their sides to 

 be throughout nearly horizontal.* 



That these beds could not have been deposited in such a position is 

 beyond question, so that the prolongation of them northward must at 

 one time have existed. What was it then, which removed all these and 



> 



*There are but few exceptions to this, due to dislocations, faiilts and folds iu the 

 strata, of purely local origin, but not of general significance in this problem. 



