154 
GEOLOGY OF THE FIRST DISTRICT. 
Gulf of Mexico, through the Mississippi and Illinois valleys, to unite with those of the St. 
Lawrence, Mohawk and Hudson valleys ; one of seven hundred feet, would also, in addition 
to all these communications, open others between the Wabash valley and Lake Erie, and 
between Lake Michigan, through Fox river, across the Portage of Wisconsin, with the Mis¬ 
sissippi valley. The summits here named are the lowest communications except the St. 
Lawrence river, between the St. Lawrence basin and New-York bay, and between the Great 
lakes and the Atlantic and Gulf of Mexico. 
Most of the ridges that seem to have been beaches of the St. Lawrence valley, in Ohio, 
Pennsylvania, Michigan, and probably also in New-York, are at an altitude of between six 
hundred and seven hundred feet above the ocean ; and most of the quaternary deposits I have 
been describing, lie at and below that level. These deposits show conclusively the existence 
of a vast inland sea, over a great extent of country that is now dry land ; and the waters 
that filled this basin have, since the communication with the Mississippi valley ceased, flowed 
to the ocean through three main channels, viz. that of the St. Lawrence, that of the Cham:- 
plain and Hudson valley, and that of the Mohawk valley, from Buffalo through the Tonawanda 
valley, and various points between Lake Ontario and the Mohawk valley. 
As it is not probable that there is less water upon the surface of the earth at present, than at 
any previous time ;* and as the ocean, by its fluidity, maintains its equilibrium, we have no 
alternative but to admit that a large portion of the American continent has been raised in mass, 
at the quaternary period, without any great alteration in the relative levels of the different 
parts, where minute examinations have been made, while the absolute elevation above its 
former level must have been from five hundred to a thousand feet. When the country shall 
have been more thoroughly explored, the absolute elevation can be determined, as the an¬ 
cient beaches show where the water level once was, and these beaches are easily recognized, 
and have been formed since the drift deposits. 
At the quaternary period, at the time of the formation of the terraces and “ lake ridges ” 
or ancient beaches, there can be no doubt that the waters of the Gulf of Mexico and of the 
St. Lawrence communicated through the Wabash and Maumee valleys ; for the summit level 
of that canal is ninety-eight feet above Lake Erie, or six hundred and sixty-three feet above 
the ocean; and the ancient beach bounding this valley on the west is one hundred and seven 
to one hundred and eight feet above Lake Erie, or six hundred and seventy-one to six hun¬ 
dred and seventy-two feet above the ocean ; so that allowing no alluvial causes to degrade the 
beach, or fill up the valley, there is a depth of eight or nine feet through which water may 
have flowed. 
It is probable that a communication also existed between Lake Michigan and the Illinois 
river, but we lack data to give certainty to it; because the beaches, if they exist, have not 
been described, or their elevation given ; and we are not certain that the amount of elevation 
* Water could have disappeared only by decomposition, and we know of no substance but water on the earth in any great 
quantity that contains hydrogen, so that the conclusion is forced upon us, that the quantity of water remains the same. 
