166 Woeikof — Cr oil's Hyjiotheses of Geological Climates. 



stract warm water from the tropics and bring it to high lati- 

 tudes. But on the 60° N. there is considerably more land 

 than on the 50° N., and air over the land under 60° 1ST. is 

 colder than over the sea. 



But to be quite sure to get beyond the influence of ocean 

 currents, I will take the mean January temperature in the 

 strictly continental climate of Eastern Siberia, under 120° E. 

 According to Ferrel's tables : 



Under 50° N. we have 0° F. 

 " 60° N. we have —30° F. 



If the January temperature decreased from 50° to 60° N. 

 according to the hypothesis of Dr. Croll, it should be on the 60° 

 N., -155° F. 



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

 hvpothesis of Dr. Croll, I take the highest January temperature 

 on the 50° N. in Ferrel's tables, that is, that on 20° E. =44° E, 

 and the coldest January temperature on the 60° N., that is, that 

 of 120° and 130 E.= —30° F. Yet, in proportion to the quan- 

 tity of heat received, the mean temperature of January on 60° 

 K should be -140° F. 



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

 sidered : 





Mean tempera- 

 ture 50° N. 



Mean tempe 



On the hypothe- 

 sis of Dr. Croll. 



r ature 60° N. 

 Actual. 



Difference. 



Mean January tempera- 

 ture of all meridians . . 



Mean January tempera - 

 ature in 120° E. (East 

 Siberia 



21-3 

 0° 



44 



-147-9 

 , — 155-3 



— 140 



1-7 

 -30 



-30 



149-6 

 125-3 



Mean January tempera- 

 ture of warmest; meri- 

 dian 50° N., and cold- 

 est meridian on 60° N_ 



no- 



If the discrepancies are so great in taking even the means of a 

 whole parallel, or strictly continental climates, and even in the 

 last example, how much must Dr. droll's calculations for Great 

 Britain be wrong? In so oceanic a climate an equal difference 

 in the amount of sun-heat will certainly cause a smaller fall of 

 temperature. 



I give another example which shows how little the method of 

 Dr. Croll is applicable even to the mean annual temperatures.. 

 In chapter IX of ' Climate and Cosmology,' he states that the 

 difference of temperature between the equator and the north 

 pole ought to be at least 200° F., if they were in proportion of 

 the heat received from the sun and the temperature of space- 



