1881.] OUO [Spencer. 



the difference of altitude above tlie water is more than 700 feet, without 

 any very eonspicucais features. 



At tlie western end of the lake, the two shores converge at an acute 

 angle. At about five miles from the apex of this angle is the low Burling- 

 ton beach, thrown across the waters in a slightly curved line, wliich forms 

 the western end of the open lake. Burlington lake, thus formed, is 

 connected with the open lake by a canal of the same name, made 

 where there was a former shallow opening between the waters within and 

 without the beach. This beach is made up of sand and pebbles (mostly of 

 Hudson River Age), and is more than four miles long, but nowhere is it half 

 a mile wide. 



No mean depth of Lake Ontario can be fairly stated. For geological pur- 

 poses it has no mean depth, because it is simply a long channel with the 

 adjacent low lands covered by back-water. 



"West of the meridian of the Niagara river the lake is evidently filled 

 Avitli more silt then eastward, as we find that the bottom slopes more 

 gradually towards the centre, where the mean depth (increasing from the 

 westward) of the channel may be fairly placed at 400 feet below the pres- 

 ent surface of the waters. In this section of the lake, the average slope 

 from both shores may be stated at 30 feet in a mile. At a short distance 

 east of the 78th meridian, the character of the late bottom changes in a 

 most conspicuous manner. Here we find a deeper channel which extends 

 for more than ninety miles, having an average depth of about 90 fathoms 

 or 540 feet, with, in some places, a trough of about GOO feet depth, gener- 

 ally near the southern margin of the 90-fathom channel. Here and there 

 is a deeper sounding — the deepest being 133 fathoms or 738 feet. The long 

 channel, surrounded by the 90-fathom contour line, is situated at a mean 

 distance of not less than twenty miles from the Canadian shore, whilst its 

 southern side approaches in some places to within six miles of the Amer- 

 ican shore, with which it is parallel. This 90-fathom channel varies from 

 three to twelve miles in width. Its broadest and deepest portion is soutli 

 of the Canadian peninsula of Prince Edwards' County. 



The mean slope of the lake bottom, from the Canadian shore to this deep 

 channel just pointed out, may be placed at less than twenty-five feet in a 

 mile, with variations from twenty to thirty feet in that distance. The mean 

 slope from the New York shore line to the 90-fathom channel may be 

 placed at sixty feet in a mile, but varying generally from fifty to ninet3' 

 feet. On examination we find that the greater portion of this slope belongs 

 to a belt which descends much more rapidly than the off-shore depression. 



That the southern side of Lake Ontario has a submerged series of escarp- 

 ments or one moderately steep and of great dimensions, is manifest when 

 we come to study the soundings. In fact, if the bed of Lake Ontario were 

 lifted out of the water, this submerged escarpment would be more con- 

 spicuous than the greater portion of the present one, known by the name 

 of the Niagara. In many places the descent from the table-land above the 

 Niagai'a escarpment is no more precipitous thtm the slopes of the sub- 



