by the Southern than by the Northern Hemisphere. 223 



greater on that hemisphere than on the northern; but notwith- 

 standing the greater rate of absorption resulting from the high 

 temperature of the surface it would not compensate for the short- 

 ness of the day. On the other hand, the surface of the ground 

 on the southern hemisphere would be colder during the long 

 night of 23 hours than it would be on the northern during the 

 short night of only 1 hour; and the low temperature of the 

 ground would tend to lessen the rate of radiation into space. 

 But the decrease in the rate of radiation would not compensate 

 fully for the great length of the night. The general and com- 

 bined result of all those causes would be that a slight accumula- 

 tion of heat would tal<e place on the northern hemisphere and a 

 slight loss on the southern. But this loss of heat on the one 

 hemisphere and gain on the other would not go on accumula- 

 ting at a uniform rate year by year, as Adhemar supposes. 



Of course we are at present simply considering the earth as 

 an absorber and radiator of heat, without taking into account the 

 effects of distribution of sea and land and other modifying causes, 

 and are assuming that everything is the same in both hemi- 

 spheres, with the exception that the winter of the one hemi- 

 sphere is longer than that of the other. 



What, then, is the amount of heat stored up by the one hemi- 

 sphere and lost by the other ? Is it such an amount as to sen- 

 sibly affect climate ? 



The experiments and observations which have been made on 

 underground temperature afford us a means of making at least 

 a rough estimate of the amount. And from these it will be seen 

 that the influence of an excess of seven or eight days in the 

 length of the southern winter over the northern could hardly 

 produce an effect that would be sensible. 



Observations were made at Edinburgh by Professor J. D. 

 Forbes on three different substances, viz. Sandstone, Sand, and 

 Trap-rock. By calculation, we find from the data afforded by 

 those observations that the total quantity of heat accumulated 

 in the ground during the summer above the mean temperature 

 was as follows : — In the sandstone-rock the quantity accumu- 

 lated was sufficient to raise the temperature of the rock 1° C. 

 to a depth of 85 feet 6 inches. In the sand the quantity 

 was sufficient to raise the temperature 1° C. to a depth of 72 feet 

 6 inches. And in the trap-rock the quantity stored up would 

 only suffice to raise the temperature 1° C. to a depth of 61 feet 

 6 inches. 



Taking the specific heat of the sandstone per unit volume as 

 determined by Regnault, at -4623, and that of sand at *3006, 

 and trap at '5283, and reducing all the results to one standard, 

 viz. that of water, we find that the quantity of heat stored up 



