QUATERNARY DIVISION. 
155 
that that part of the country has experienced at that epoch, is the same as that around Lake 
Erie. If, however, we suppose it to be the same, it is probable that a great volume of water 
passed between Milwaukie and the south end of Lake Michigan, the lowest point of depres¬ 
sion being near Chicago, and elevated only seventeen feet above the lake, or five hundred 
and ninety-five feet above the ocean, and would give a depth of water in the lowest point of 
seventy-six to seventy-seven feet, between the waters of the Gulf of Mexico and the St. 
Lawrence. 
It has been shown that the gulf stream must, from the operation of general causes, have been 
forced upon our coast before this elevation of the quaternary ; and then, as now, it must have 
elevated the waters of the Gulf of Mexico* above the ordinary ocean level. A portion of 
this would necessarily flow through the channels of communication between the valley of the 
Mississippi, which was once a gulf, and the basin of the St. Lawrence. This is the only 
way we can account for the currents that have flowed through the Mohawk, Champlain and 
Hudson valleys during the quaternary period ; because, when so much of the St. Lawrence 
basin was covered by water, the water derived from rain, snow, and the drainage of the sur¬ 
rounding country, would not be much more than sufficient to compensate for its evaporation. 
So at that time, when the lakes were one sheet of water communicating with the Atlantic 
through many channels, the probability is that there would be but little current, except what 
would be due to tides, and these would be in opposite directions. During this period, the 
clay beds were probably deposited. If, however, the gulf stream caused a flow into Lakes 
Michigan and Erie from the Gulf of Mexico, it would account for the general course of trans¬ 
port of the deposits of the quaternary period in the Hudson and Mohawk valleys. The de¬ 
posits of this formation are so similar through the whole of the St. Lawrence basin, and the 
Mohawk, Hudson and Champlain valleys, that they must all be referred to one general cause. 
The clays are marly; and throughout almost the whole southern border of this basin, the 
waters were in contact with calcareous rocks. 
The upheaving action by which these depositions were elevated above the ocean level, 
caused the largest portion of the waters of this basin to drain off down to the present level, 
through the channels mentioned, namely, the St. Lawrence river, and through the Mohawk, 
Champlain and Hudson valleys. This would account for the greater acceleration of the 
currents, and the deposition of coarse materials, at the close of the quaternary period; for 
the outlets through the Highlands, the Walkill and Mamakating valleys, through the Cham¬ 
plain valley at the summit, and the Mohawk valley at the Little falls and the Noses, were 
limited in their capacity for drainage for so great a volume of water; and if the uplift was 
sudden, the rush of water through the narrow channels would necessarily be very violent, and 
from the quantity of water to be discharged, long continued. This would also account for 
* The general contour of the coast was undoubtedly, in form, an approximation to what it now is, with the Cumberland 
mountains forming the southwestern cape, as the south end of Florida does at present, while the gulf extended far up the Mis¬ 
sissippi and its tributaries. 
