64 EF. W. Ailgard—Later Tertiary of the Gulf of Mexico. 
waters of the Gulf, in the deep wells of Calcasieu; and the 
loess lies at a similar height above the sea-level, not many miles 
above the head of the Mississippi Delta. 
_ The inference is irresistible, that the upward movement of 
the Tertiary period continued up to the end of the Glacial 
poch, whose gravel could not be carried far beyond the shores 
of the Gulf. It is clear, also, that even a minimum elevation 
of 450 feet, so far proven, would convert the Gulf border, to 
the edge of the 100-fathom line, into a region of shallows, 
900 feet above the sea, and in the reverse movement, of the 
Champlain epoch, they were again covered by the loess and 
surface loams, to be re-elevated during the “Terrace” period of 
erosion, by which the present channel of the Mississippi River 
was formed. 
The map of soundings exhibits very strikingly the analogy 
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