Sayles — Dilemma of Paleoclimatolo gists. 461 



been settled by the physicists of the past with a confident 

 answer that the heat from the earth's interior is a negli- 

 gible quantity. What would our surface temperatures be 

 if by some magic the ice from the poles should suddenly 

 be melted away? It would appear that both of these 

 questions must be answered satisfactorily before we can 

 make progress with the glacial period riddle, and the 

 warm period riddle. 



If the earth receives at the surface more heat from the 

 interior than we are aware of, the place to look for it is 

 evidently in the oceans rather than on the continents. 

 When we consider the tremendous mass of ocean water, 

 all of which is supplied with heat in excess of 493 degrees 

 F. in temperature above absolute zero, it is difficult to con- 

 ceive of the sun as the sole agent of the heating. There is 

 no zonal arrangement of temperature along the ocean bot- 

 toms, where the temperature rarely goes below the freez- 

 ing point, and it looks very much as though the earth must 

 prevent any lowering of the heat below that point. There 

 are several things which point to the earth as the heating- 

 agent for at least part of the heat of the waters. For a 

 long time such heat has been suspected. The geothermal 

 gradients along the coasts, as shown by the records of 

 deep borings, are not as much depressed as they should be 

 if the oceans have cooled off the upper part of the crust 

 close to the oceans. At a depth of two miles below the 

 surface of the continents and with a thermal gradient of 

 60 feet to a degree rise, there should be a temperature of 

 about 680 degrees F. above absolute zero in middle 

 latitudes. We do not know what the temperatures of 

 the rocks are in the ocean bottoms at a depth of two miles 

 from the bottom of the waters. Is it possible that they 

 have lost 187 degrees in heating the waters? Murray 16 

 records some observations on this point. He says : 



"Some such increase of temperature towards the bottom has 

 long been suspected as an effect of the internal heat of the earth ; 

 as early as about 1840 Aime looked for it, but his methods were 

 not sufficiently accurate. More recently, several indications of 

 a rise of temperature towards the bottom have been observed. 

 The pressure and the internal heat having the same effect, it is 

 difficult — at our present stage — to determine how much is due 

 to the internal heat of the earth. In any case the bottom water 

 temperatures would be considerably lower but for the effect of 

 pressure on the sinking waters." 



