2G8 



ON THE HYDROLOGY OF THE BASIN 



shoals and dangers of the navigation, — a sort of parallel repetition and model of the sur- 

 face of the bottom. 



The circumstances which have been here related occur again at most of the Rapids ; 

 and there are interesting illustrations every year at Lachinc, — on no occasion or place more 

 so than the remarkable shove which took place last December, four miles above Montreal, 

 also at Cornwall, and in other Rapids up stream. Similar effects take effect on the river 

 in the Richelieu Rapids, below Lake St. Peter, which generally rises far above; its usual 

 level, and causes considerable inundation in the district above this part of the river, and 

 on both sides of it. 



Rut perhaps the most striking feature of the season is its breaking up, which is gener- 

 ally attended with the same features on even a more extended scale, the average period of 

 this being about the 10th of April; and at Montreal it has been accompanied by many 

 curious effects, of jamming and shoving, and what is more important, by certain occasion- 

 ally attendant floods, so as to render it a matter of surprise, in spite of repeated warnings, 

 and with a past history of the river, which nature has painted in such distinct and marked 

 lines as cannot be misinterpreted, — that the subject of a remedy has not long since met 

 with more becoming attention from the authorities of the city, especially in the interest 

 of a portion of it extending towards the Lachine swamp, which bears marks of its ancient 

 office, as an important channel of the river. 



The breaking up is always accompanied by the shoving, and generally with more or 

 less packing, The photograph accompanying this paper (Appendix, marked 8) , illustrates 

 truthfully the evil to be contended with, in a special instance which was observed in 1859. 

 In these movements are tested the value of the cribwork elsewhere described. The 

 wharves being kept low, they are comparatively clear of the moving mass of ice ; and if 

 sufficiently loaded with stone, and left with smooth surfaces, no considerable injury results. 

 Instances of the removal of large masses of cribwork, although known, arc rare ; and 

 where they have occurred, the fact lias generally arisen from want of attention to their 

 loading, to their undue height, or to injudicious position or direction of their sides. 



The tidal portion of the river occasionally « takes" at the Richelieu Rapids ; and in 

 about four years out of five it takes for a few days, at least, and sometimes even for the 

 whole time, in the narrow gorge of the river, opposite Caronge, from six to eight miles 

 above Quebec. 



At Quebec the much wished for '■ taking," and the formation of a " pont," so called, is 

 less frequent; and it seems that one year in four is about the frequency of occasions. 

 When the ice bridge or "pont" exists, the surface is generally frozen for a considerable 

 distance to the head of, and sometimes down both channels of the river at the sides of, 

 the Island of Orleans, from one to six miles. 



