462 Canadian Record of Science. 
bay. Capt. Fleming, of the steamer James Swift, informs 
me that it comes and goes, and is so well known that when 
his boat happens to ground, through missing the channel, 
he simply waits for the “ tide” to again float it. During a 
continuous calm of two or more days the rise and fall cease. 
It is an interesting fact that the summit levels of the dif- 
ferent systems of lakes which are the sources of the water 
supply of the Rideau Canal lie chiefly in the townships of 
Bedford and Loughborough, and within a very moderate 
distance of Lake Ontario. The headwaters of the Lough- 
borough Lake system are within seven miles of Kingston ; 
Knowlton, the uppermost of those lakes which find an out- 
let on the canal at Mud Lake, is within thirteen miles of 
the same place; whilst Bobb’s Lake (a corruption, perhaps, 
of Robb’s Lake), the most important of the higher levels of 
the River Tay system, whose waters eventually reach the 
Ottawa, is also situated within twenty-five miles of Kings- 
ton. The low, broad ridge of gneiss which connects the 
Laurentian rocks of New York State with the main range 
in Canada, forms the watershed here of the streams falling 
into the Ottawa, on the one hand, and the St. Lawrence 
and Lake Ontario, on the other. The strata are, however, 
thrown up into very numerous subordinate ridges, which 
lie here in directions generally north-east and south-west, 
and somewhat parallel to each other. These ridges, pro- 
longed far to the south-west towards Kingston, have led to 
the formation and extension of lake basins in that direction. 
Those who planned the Rideau Canal, notably Col. By, 
showed their engineering skill in taking advantage of the 
number and different levels of these lake basins to procure 
an adequate supply of water for navigation on the summit 
level as well as on both slopes, causing the waters some- 
times, as in the Loughborough Lake and the Devil’s Lake 
systems, to almost double on themselves. 
This great water system, including in it fifty-three lakes 
which are from one to fifteen miles long, has another pecu- 
liarity, that these lakes lie, with only four unimportant 
