70 Major Lachlan on the Rise and Fall of the Lakes. 
warm, dissolves it at once. Hence it will generally be found that 
after a very severe wien the waters of the Lakes will be much 
higher than at other tim Heavy gales also raise the water in 
the upper parts of the cain aud also cause currents in various 
directions. ‘The rise, however, in Lakes Superior and oe 
from this or any other cause, never exceeds a few 
Whether a gradual diminution of the waters “of Lake superior is 
now going on, is a point on which no one is qualified to give an 
opinion ; for vo observations have been made or recorded to ascer- 
tain the interesting fact. Any diminution must be always imper- 
ceptibly gradual, and would require constant, accurate, and regu- 
larly recorded observations during a great number of years to 
render this indisputable. The streams which discharge into 
Lake Superior amount to several hundreds in number, and the 
quantity of water supplied by them is many times greater than 
that discharged at the falls of St. Mary, the only outlet. There 
is, however, no reason to imagine from this that the quantity of 
water increases; for it is absolutely necessary that there should 
be a supply very far exceeding the discharge, to replace the 
inimense expenditure arising from the evaporation from so exten- 
sive a surface.” 
Adhering to my intention of reserving for the present .any com- 
ments on the above, as of other quotations, I now revert to the 
next isa writer on this important subject, namely, General 
Dearborn, who, in the 16th volume of the American Journal of 
Saisie; cairo referred to, observes that “it is not sufficiently 
certain ra tides may not be produced in the great chain of 
Lakes, in the same manner as they are in the ocean;” and in 
proof cenne? quotes an elaborate theory of the distinguished Dr. 
Young (illustrated by three diagrams) which had at that time 
been sanctioned by the scientific for more than twenty years, n 
only presuming the possible existence of such tides, but fornishiig 
the means of demonstrating thatsuch is the fact in deep and bro 
Lakes, and even going so far as, where the area and depth of a 
lake is known, to givea theorem by which the maximum rise 
and fall of the waters and the time of its oscillation, or in which 
a tide wave might pass over it, can be ascertained.* But the 
General at the same time admits, with regard to ‘the periodical 
increase and diminution of the whole volume of water in the 
kes.” that he is in possession of no definite facts, save what 
was contained ina letter from Captain Dearborn, stating, that 
whilst stationed at the Sault Ste. Marie, on Lake Superior, he 
had himself observed for three successive days an ebb and flow 
of one-and-a-half feet, in the conrse of about two-and-a-half hours 
—. Dut ey he Hesated it to the winds; and that he sup- 
Philosophy, ib ELE Pinca sage Mekenh. ee 
