174 NOTES ON ANCHOR ICE. 



winter elevation of a mighty river, where it is beyond the tidal influ- 

 ence, and while its volume is daily diminishing, will be found in a 

 paper " On the Packing of Ice in the River St. Lawrence," by Sir 

 William Logan, published in the Transactions of the Geological 

 Society of London for 1842. 



This rise of the river — at least so far as to secure the formation of 

 a winter road in front of the city — has always been viewed with satis- 

 faction rather than alarm, and is confined to the section below the 

 Lachine Rapids. Above the Rapids the level is uninfluenced by the 

 annual icepacks below it ; and as the current is very strong, — the fall 

 between Lake St. Louis and the head of the rapids being about three 

 feet per mile average — the river is open throughout the winter, and is 

 navigated by a steam ferry-boat between Lachine and Caughnawaga. 

 But, in the latter part of January, 1857, after a cold "term" of 

 unexampled severity and duration — long after the ice had taken oppo- 

 site the city, and when, according to all previous experience, no far- 

 ther rise was to be apprehended, either above or below the rapids, 

 until the "breakup" in the spring — the River, above the Lachine 

 Rapids (where it is always unfrozen,) rose suddenly four to five feet, 

 pouring an Arctic current down the aqueduct of the new Water Works. 

 A few feet more of elevation would have sent the river over its banks,, 

 and the consequences might have been most serious. 



Such intense cold was followed, as is usual, by a rapid rise of tem- 

 perature, whereupon the water fell about two feet, but thereafter re- 

 mained for weeks at least two feet above its ordinary level. 



There is a tradition of something similar having occurred about 

 seventy years ago, but this was not heard of until after the irruption ; 

 all recent experience and inquiry going to shew that after the ice has 

 taken, the water in this reach lowers gradually with slight fluctua- 

 tions until the spring. 



This flashing above the rapids was independent of any movement of 

 the fixed ice below, either opposite Montreal or in the Laprarie Basin, 

 the levels of which remained undisturbed. Another peculiarity was — 

 the absence of any visible cause ; no ice had descended or was descend- 

 ing, and on the surface nothing but blue water -was to be seen. The 

 continuous descent, for days and weeks before the river is frozen over 

 above the city, of large masses of ice which being arrested below 

 would dam back the water, is sufficient to account for the rise at Mont- 

 real ; but in this case there was no descending ice, the Lake St. Louia 



