Major Lachlan on the Rise and Fallof the Lakes. 171 
to the northwest angle of Lake Superior, embracing all the coun- 
try whose streams are tributary to the Lakes, the surface drained 
is calculated (as shewn by a table of sections) at 248,775 square 
miles, besides 86,760 square miles occupied by the Lakes; and it 
is further calculated that the enormous accumulation of water dis- 
charged through the River Detroit during high floods, allowing 
acurrent of only one mile an hour, is not less than 95,135,000 
cubic feet per hour, or 1,585,558 cubic feet per minute. The 
floods on Lake Ontario, however, are generally the highest by 
about two feet; and for this obvious reason, that it receives the 
successive accumulations of all the Lakes, from the Niagara to 
r. 
testimony to be adduced: “The preceding year (1840) was the 
second since the unusual elevation of the waters of the Lakes, 
since which time there had been a remarkable coincidence in the 
tatios of subsidence, the more unlooked for when taken in con- 
hection with the causes which tend to equalize the amount of 
falling water in the form of rain, snow and dew, with the con- 
stant action of evaporation.” : fet ag ot & 
“The diminution in a given quantity of water exceeds by 
Such expanded areas of water, subject to such influences should 
be greatly affected. The wonder is that they do not oftener 
Present greater fluctuations. ‘The equal and almost unvarying 
“The semi-annual alterations observable in summer aud win- 
ter arise from other well known causes. In summer the supply 
's unchecked, and the consequence is an increase to the height of 
®xactly the semi-annual fluctuations have never been thought 
neccessary. Besides it is not uncommon for ice in large bodies 
‘0 collect at the outlets of the Lakes, and for a time prevent the 
usual discharge, as was the case at the outlet of Lake Huron in 
Connection with a west wind in 1824 and 1831, when the depth 
in the Detroit River opposite the City of Detroit was diminished 
over ten feet.” * * * * oS 
