W. J. McGee—Thickness of Ice-sheet at any Latitude. 267 
all the water of the globe amounts to only 335,500,000 cubic 
miles or but little more than three-fifths of that required to form 
the assumed ice-cap. 
If the above estimate seems too large, let it be reduced by 
seven-eighths, which will bring it well within the bounds pre- 
scribed by more moderate advocates of the theory; but even 
then it is too large to be admissible; for it would require one- 
fifth of the water of the globe to form even the smaller ice-cap. 
But diminishing the water of the globe one-fifth would diminish 
the water-covered area by a considerably larger fraction; for 
the sea bottom does not descend uniformly to the deeper abysses. 
The slope is, usually, gentle for a considerable distance from 
the shore, and then steep and precipitous to the abyssal depths. 
Reducing the water one-fifth would therefore reduce the area 
or influence the motion of middle-latitude glaciers, can never 
have taken place in this hemisphere. 
