172 DALY. 



appear to be of the order of magnitude noted for these averages in the 

 case of the Antarctic ice-cap. 



The dimensions of the vanished Pleistocene ice-caps are discussed 

 in the wi'iter's 1910 paper.^^ Therein an average thickness of 3,600 

 feet (1,100 m.) and a total area of 6,000,000 square statute miles 

 (15,500,000 square km.) were assumed, and these values still seem to 

 the writer to be of the right order. 



The uncertainties as to extension and thicknesses of the great ice- 

 caps, both Pleistocene and modern, make it unnecessary to consider 

 at all the many smaller areas of glaciation, which are thus of no sig- 

 nificance in the present problem. Similarly, the displacement of 

 sea-water by those parts of the ice-caps which grew into shallow, 

 epicontinental seas is relatively small and may here be neglected. 



For convenience the various rough estimates are indicated in the 

 following table. 



Estimated areas, in square kilometers. Estimated average thickness, in meters. 



Present. Pleistocene. Present. Pleistocene. 



Minimum. Maximum. Minimum. Maximum. 



Antarctic 13,000,000 16,000,000 300 1,000 (?) 600 1,800 (?) 



ice-cap 



Greenland 1,900,000 2,500,000 (?) 300 1.000 (?) 400 (?) 1,500 (?) 

 ice-cap 



Vanished ■ 15,500,000 1,000 1,500 (?) 



Pleisto- 

 cene ice- 

 caps 



14,900,000 34,000,000 



According to the estimates, the existing ice-caps represent approxi- 

 mately 4,500,000 to 15,000,000 cubic km. of ice, corresponding to 

 about 4,000,000 to 13,500,000 cubic km. of water. The area of the 

 whole ocean is nearly 361,000,000 square km. Hence, to form the 

 existing ice-caps, its average level has been lowered below that of an 

 ice-free earth by an amount lying between 11m. and 37 m. 



Assuming simultaneous maxima for the major European, Labrador- 

 Keewatin, Cordilleran, Greenland, and Antarctic sheets during the 

 Pleistocene, the total ice formed was 26,000,000 to 56,000,000 cubic 

 km., corresponding to about 23,500,000 to 51,000,000 cubic km. of 

 water. The general sea-level would thereby be sunk below that of an 



21 Amer. Jonr. Science, 30, 300 (1910). 



