Woeikof — CroWs Hypotheses of Geological Climates. 165 



firmed by the late observations of the Russian polar station of 

 Sa^astyr, at the mouth of the Lena.* 



Dr. Croll returns over and over to the importance of knowing 

 the temperature of space, as well in 'Climate and Time' as in 

 his new book, and in the latter he is rather in favor of a lower 

 value for it than that of Herschel and Pouillet, which he adop- 

 ted in ' Climate and Time.' He thinks this knowledge "of the 

 utmost importance for the determination of the temperatures 

 which obtained during high eccentricity and winter in aphe- 

 lions, and repeatedly he admits that the temperature of a place, 

 other things being equal, is proportional to the heat received 

 from, the sun. To make us quite sure of his meaning, he has a 

 table in ' Climate and Time,' p. 320, where he gives the value of 

 excentricity for different periods, and the midwinter tempera- 

 ture of Great Britain for periods of great excentricity and win- 

 ter in aphelion. So for example it was, according to him : —6*03° 

 F. 850,000 years ago, when the excentricity was 0-0747 ; 1'03 F.° 

 210,000 years ago, excentricity 0"0575, etc. The temperatures 

 of Great Britain are evidently given only as an illustration, and 

 there is no doubt that a similar decrease of temperature was 

 experienced, according to him, even in the midst of the Atlan- 

 tic Ocean. Admitting even the present mean winter tempera- 

 tures there to be 6° F. higher thaa in Great, Britain at the same 

 latitude, we would then have, at the highest excentricity with 

 winter in aphelion —603° F. and 407° F. 210,000 years ago; 

 that is, temperatures which were possible only if the ocean were 

 covered with solid ice, which is an impossibility with anything 

 like the present geographical conditions ; and Dr. Croll repeat- 

 edly admits that they have not changed since the glacial epoch. 



It is strange that Dr. Croll has not tried how his method 

 works when applied to the existing mean temperatures of dif- 

 ferent latitudes. The mean temperatures from 10° S. to 10° N". 

 have been calculated by different scientists; I use the calcula- 

 tion of Ferrel as the most recent. The mean temperature of 

 January can be considered as the result of the position of the 

 earth toward the sun at the winter solstice. Thus if we com- 

 pare the mean January temperature of 50° and 60° N. we have 



50° N. 21-3. 60° N. 17. 



The quantity of solar heat received at the winter solstice on 

 the 60° N. is but 0'35 of that on the 50° K Thus, if the tem- 

 perature of the former was less in proportion to the quantity of 

 solar heat received it should be —147° F. It is easy to see 

 how large the discrepancy is. 



Dr. Croll ascribes the relatively small decrease of tempera- 

 ture with latitude to the influence of ocean currents, which ab- 



* Izviestia of the I. Russ. Geogr. Soc, 1885, N. S. 



