Conditions favorable to Glaciation. 



105 



and the curves shown in figures 2 and 3, enable one to judge 

 sufficiently of the climate of zero eccentricity. The winter in 

 the northern hemisphere would be a little cooler throughout and 

 the temperature gradient a little smaller. Other things being 



Figure 3. 



Heat rates for each of the great seasons under various conditions. The curves 

 N and n represent the present obliquity and zero eccentricity. They also appear 

 in figure 2. The curves X, and x show the rates for greatest eccentricity and 

 winter of maximum length in the northern hemisphere The curves B and b dis- 

 play the rates for an obliquity of 24° 36' with zero eccentricity. 



the same, the winter precipitation would be somewhat smaller, 

 but more of it would fall as snow. In summer the July tem- 

 perature would be two or three degrees F. higher than it now 

 is, and the heat gradient would almost imperceptibly exceed 

 the present. On the whole the normal weather would proba- 

 bly be within the range of present experience or, in other 

 words, the winter would be what is now considered a cold one, 

 and the summer such as is now thought unusually warm in the 

 northern hemisphere ; but the seasons would not be so extreme 

 as they would now be in the southern hemisphere were the 

 distribution of continental areas there the same as it is in the 

 northern hemisphere. 



Having established a climate of zero eccentricity it may be 

 compared with the extreme climate of highest eccentricity. 

 It appears from diagram 3 and the table that the winter of the 

 eccentric period in the rigorous hemisphere would be intensely 

 cold as compared with that of the period of zero eccentricity, 

 but it is important to observe that the difference would be 

 most marked in the tropics. It is not needful to depend on 

 my formulas or tabulated values of heat rates to assure oneself 



