276 



ON THE HYDROLOGY OF THE BASIN 



Duck Islands, when it was found that while the air was 64°, the water showed 52° at 

 surface, and 42° at 100 fathoms depth. 



The fact of the existence of the cooler water being always available on Lake Ontario, 

 has long been known to those who navigate the lakes ; and advantage is constantly taken 

 in summer of the means always within reach, to obtain a supply of cool water in a vessel 

 let down for a few minutes to the depth of a few fathoms below the warm surface water 

 of the lake. 



ILOO DS. 



Attention has been drawn to the remarkable absence of floods in the River St. 1 Law- 

 rence. Although those in the Ottawa are felt, yet they rarely exceed seven feet in the 

 greatest instance, the whole basin forming an exception to the general rule of all North 

 American rivers. In fact, taking the St. Lawrence River proper, from Lake Ontario 

 downwards, it is most remarkable that, except under the influence of the packing of the 

 ice (the effects of which are elsewhere explained), the floods in the river, due to freshets, 

 are scarcely perceptible; the extreme fluctuation which generally takes place in the 

 months of April and May being about two feet two inches above the normal level. This 

 is, of course, due to the compensating effect of the great lakes, the area of the rivers 

 themselves, and the uncounted lakes and swamps scattered over the whole of the basin 

 on the slope of the northern side of the drainage area. And it is not a little remarkable 

 that these lakes appear to be most numerous in the Laurentian system. The same feature 

 is observable in the Adirondack region, which is also full of streams and lakes, many of 

 winch are found at seventeen hundred to eighteen hundred feet above tidewater at the head 

 of the Moose River, and the Black River, naturally draining into Lake Ontario, at Sackett's 

 Harbor, and lying closely contiguous to the head waters of the Scroen and Mohawk, 

 flowing to the Hudson, and those of the Raquette, which drains into the St. Lawrence, 

 at Cornwall. 



A glance at the map will suggest the contrast which the author now begs to make in 

 reference to the drainage of contiguous basins. 



If we examine the basin of the Ohio (the southern neighbor of the; St. Lawrence), 

 draining the northeast portion of the Mississippi basin, and having its source from five 

 hundred to one thousand feet above the level of Lakes Ontario and Erie, the dividing 

 ridge not averaging thirty miles away from the shore of both of them, and having an area 

 of about two hundred thousand square miles, one is struck with the remarkable contrast 

 in its discharge. The river flows for its entire length (about nine hundred miles), in its 

 low state with a gentle current, unintercepted by rapids, except at the Falls of Ohio, near 

 Louisville, where there is a sudden fall of twenty-six feet in three miles; and it is during 



