614 CVROS Fa TOLMAN, 
(viz. those with temperature of 2°-3° C.) will advance south- 
ward at least as far as the southernmost limit of the ice-sheet. 
Therefore, we have started the line a 0 at 60° N.and S. latitude . 
(the latitude of the southern Greenland glaciation) and the line e 
h at 37° (the latitude of the southernmost Pleistocene glaciation 
in North America). With this postulated southern advance of 
the cold waters, there must also have been a rise of these cold 
waters toward the surface. The amount of this rise is undeter- 
minable at present. But since we have used Dr. Arrhenius’ 
estimate of a drop of 5° in the temperature of the surface waters, 
we may assume the same fall of temperature for the body of the 
ocean. A given fall in temperature of the surface water must 
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Fic. 6.—Section of ocean from north to south pole. Ocean taken at average 
depth of 2000 fathoms. Portion below 1500 fathoms has temperature below 2° to 3° C. 
Line adc incloses section of ocean whose temperature is now above 2° to 3°. 
Line e fA limits the equatorial and upward migration of the polar waters during maxi- 
mum Pleistocene glaciation, when the ice reached the latitude 37° N. 
Line m & x ditto for waters with Pleistocene temperature of 2° to 7°. 
Above line # & # ditto for water of higher temperature. 
take a very long time to communicate itself throughout the body 
of the ocean, but the larger the period during which the surface 
waters maintain their low temperature the more completely does 
the body of the ocean lose its extra heat. 
At 1500 fathoms the temperature of the temperate and 
equatorial waters is 2°-3° C. above zero; therefore, the maxi- 
mum depth which the line a—c reaches is placed at d. At 300 
fathoms the warm waters have a temperature of about 7°. 
Therefore, we place here f on the line ef, designating the 
maximum advance upwards of the polar waters. 
Point & on m-k-n is 150 fathoms below the surface and at that 
‘ All temperatures calculated from tables of temperatures, given in Vol. I of the 
Challenger Reports. 
