THE CAUSE OF THE GLACIAL PERIOD. 



479 



But to be quite sure of taking the most favorable case for 

 the hypothesis of Dr. Croll, I take the highest January tem- 

 perature on the 50° north in Ferrel's tables, that is, that on 

 20° east =44° Fahr., and the coldest January temperature on 

 the 60° north, that is, that of 120° and 130° east,= —30° Fahr. 

 Yet in proportion to the quantity of heat received, the mean 

 temperature of January on 60° north should be —140° Fahr. 



The following table gives the results of the three cases con- 

 sidered : 





Mean tem- 

 perature 



50° N. 



213 



0° 



440 



MEAN TEMPERAT 



On the hypothe- 

 sis of Or. Croll. 



CTRE, 60° N. 



Actual. 



Difference 



Mean January temperature 

 all meridians 



of 



— 147-9 



— 1553 



— 140-0 



1-7 

 -30 



— 30 



149-6 



Mean January temperature 

 120° E. (east Siberia) 



in 



125-3 



Mean January temperature of 

 warmest meridian 50° N., and 

 coldest meridian on 60° N 



110-0* 



These facts, and many others like them, make it evident 

 that we understand very little about the laws governing the 

 distribution of heat over the surface of the earth. Other 

 things besides ocean-currents are active in the matter, and 

 some of them must be far more potent than any cause which 

 we now clearly discern. We quote again the words of the 

 same high authority : 



How can we judge of the change of temperature resulting 

 from this or that distance from the sun, even if we knew accu- 

 rately the temperature of space, when we do not know the dia- 

 thermancy of the atmosphere under different conditions ? We 

 know only that it is exceedingly different, according to the 

 different quantities of carbonic acid and aqueous vapor con- 

 tained in it, and in a far higher degree, according to the ab- 

 sence or presence in different quantities of suspended liquid 

 and solid particles (clouds, dust, smoke, etc.). Thus, when 



Woeikoff in u American Journal of Science," vol. cxxxi, p„ 166. 



