Conditions favorable to Glaciation. 



103 



Heat-rates for Northern Summer. 



Lat. 



P 



N 



N 



B 



0° 



0-9397 



0-9592 



1-0626 



0-9552 



10 



0-9945 



1-0150 



1-1245 



1-0144 



20 



1-0216 



1-0427 



1-1552 



1-0457 



30 



1-0208 



1-0419 



1-1543 



1-0489 



40 



09930 



1-0135 



1-1229 



1-0245 



50 



0-9411 



0-9605 



1-0642 



0-9762 



60 



0-8721 



0-8901 



0-9862 



0-9111 



A 



0-8270 



0-8441 



0-9352 



0-8768 



70 



0-8115 



0-8283 



0-9176 



0-8587 



SO 



0-7869 



0-8032 



0-8898 



0-8381 



90 



0-779S 



0-7959 



0-8818 



0-8326 





Heat-rates for Northern 



Winter. 





Lat. 



P 



n 



X 



b 



0° 



0-9797 



0-9592 



0-8785 



0-9552 



10 



0-8955 



0-8768 



0-8030 



0-8698 



20 



0-7869 



0-7705 



0-7057 



0-7610 



30 



0-6577 



0-6439 



0-5898 



0-6326 



40 



0-5127 



0-5019 



0-4597 



0-4893 



50 



0-3583 



0-3508 



0-3213 



0-3384 



60 



•0-2051 



0-2009 



0-1840 



0-1901 



A 



0-1164 



0-1140 



0-1044 



0-1198 



70 



0-0821 



0-0804 



0-0736 



0-0764 



80 



0-0198 



0-0194 



0-0177 



0-0182 



P and p stand for present obliquity, eccentricity and length of seasons. 



N and n stand for present obliquity, 23° 27', and zero eccentricity. 



X and x stand for present obliquity, eccentricity = 0-0745, and greatest differ- 

 ence of seasons. 



B and b stand for obliquity = 24°36' and zero eccentricity. 



N", n, B and b are computed from the formulas developed in the note appended 

 to this paper which P, p, X and x are derived from N. and n as explained in the 

 text. The rates for the southern hemisphere, shown in diagram '6, are identical 

 with those in the northern hemisphere except in the case of greatest eccentricity 

 when they are multiples of those in corresponding northern latitudes. 



A represents the latitude of the arctic circle, or 66° 33' in all cases excepting 

 those of B and b for which A = 65° 24'. 



vapor increases much more rapidly than temperature* and so 

 also must the rate of evaporation. On the other hand the cold 

 in high latitudes must be great to promote condensation in the 

 form of snow ; besides which the temperature gradient should 

 be high or steep because the energy available for wind, and for 

 water currents due to winds, is in direct proportion to the 

 difference of temperature. The great foe to glaciation in sum- 

 mer is rather warm rain than sunshine, for warm rain represents 

 heat transferred from lower latitudes to higher ones. A cer- 



* The tension is a function of the temperature, and this function is not linear. 



