410 
GEOLOGY OF THE FOURTH DISTRICT. 
we have no other mode of explanation left than the one suggested. The existence of rocky cliffs 
along the lake shores is likewise evidence of the same fluctuating elevation in the waters. 
The annual fluctuations in the level of the lakes are doubtless due to the nature of the 
seasons, depending on the quantity of rain and snow and the amount of evaporation. But 
it is not so satisfactorily demonstrated that for a series of twenty years the quantity of rain 
and snow has increased, or that evaporation was lessened uniformly throughout this period.* 
The effect of winds in producing temporary elevations and depressions of these lakes is 
very remarkable. A strong westerly wind will raise the water in the eastern end of Lake 
Erie several feet in a few hours; a much larger quantity is driven down the Niagara river, 
and although so rapid a stream below the falls, the water frequently rises fifteen or twenty 
feet during a westerly wind. At the same time the water in the lake is diminished at the 
western extremity, and a corresponding depression takes place. The prevalence of a strong 
easterly or northerly wind, in the same way, drives the water to the western and southern 
parts of the lake, and a much smaller quantity flows down the Niagara river during such a 
period. The same effect takes place in a greater or less degree in all the lakes; the rising at 
one extremity and sinking at the other, till the wind subsides, when it resumes its equilibrium, 
and in so doing presents a beautiful exhibition of the long swells which are observed in the 
ocean after the subsidence of a high wind. 
The relative situation and elevation of these large and small bodies of water, with the rivers 
and lakes of this and other parts of the State, have largely contributed to place New-York in 
her exalted commercial relations with the surrounding country. The valleys of the Hudson 
and the Mohawk have opened a passage through two ranges of mountains, by which the waters 
of Lake Erie are mingled with those of the Atlantic, affording by the artificial means an easy 
navigation from the one to the other. Again, the waters of the upper Hudson are turned into 
the Champlain canal, on its summit level, and mingle with the Atlantic in the Gulf of St. 
Lawrence instead of the Bay of New-York. The waters of the Tioga river are turned from 
their natural course, through the Chemung canal; and instead of flowing by the Susquehannah 
into the Chesapeake bay, now pass by Seneca lake into Ontario, and thence into the Gulf of 
St. Lawrence. Far to the westward again, by the Illinois canal, the waters of Lake Michi¬ 
gan are destined to mingle with the Mississippi. Man has here done much to accomplish all 
these changes; but before man began, nature had done more, and to her are we indebted for 
those facilities which no other portion of this or any other country enjoys. 
* I had collected some facts to prove that the former condition of the great lakes was, in some degree at least, influenced by the 
elevations and depressions which have taken place along the eastern portion of our continent, extending sometimes as far as 
these lakes. Other subjects, however, have so occupied my time, that nothing more than a crude hypothesis could be offered, 
and therefore the subject is left for a future opportunity. 
In connexion with this subject, I have learned from the early navigators of the Hudson river, that forty years since, the influence 
of the tides was not felt at Albany ; but since that period they have been gradually advancing, so that at present the difference 
between high and low water is about two feet. This is alleged to have improved the navigation at some distance below Albany, 
so that what were formerly difficult places to pass, now afford sufficient depth of water. This circumstance bears strongly upon 
the modem accumulation of silt below Albany, which now obstructs the navigation at certain seasons. If from any circumstance 
the tide has been gradually advancing up the river, the point of deposit of these light materials, being at the meeting of the 
stream and tidal wave, would likewise take place at a higher point in the river. This is a subject of great interest, and as con 
nected with the evidence of a former greater elevation of water in the Hudson river, is worthy of attention. 
