J£*2frtk&%£ 



THE 



AMEBIC AN JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



Art. XVI. — Examination of Dr. OroUs Hypotheses of Geological 

 Climates ; by Dr. A. Woeikof, of St. Petersburg. 



The hypotheses of Dr. Croll have attracted so general atten- 

 tion in the last ten years, not only in Great Britain, but also in 

 the United States and other countries, that a review of them 

 by a meteorologist is, I think, desirable. This work is very 

 timely now, because Dr. Croll has just published a new book on 

 the subject* in which he further explains and extends his views 

 and answers his critics ) and besides he mentions in the preface 

 the fact that he wishes to devote the following years to work 

 in a wholly different direction. Thus we have now before us a 

 system as complete as it is likely to be made by the author. 

 It is not my aim to review the whole work of Dr. Croll on 

 glacial Geology and Cosmology, but only to consider some 

 points of it which are within my line of study. 



In his answer to Prof. Newcomb, Dr. Croll discusses the 

 mean temperature of land and ocean, f and arrives at the start- 

 ling conclusion that " the ocean must stand at a higher mean 

 temperature than the land." Now, since the mean and not sur- 

 face temperature is mentioned, the meaning of the author is, it 

 seems, clear, but the result is entirely opposed to what we know 

 to be true. Not only have the ocean?, which receive cold 

 currents from polar seas, a much lower mean temperature^ than 



* Climate and Cosmology. Edinburgh, 1885. f Page 26 and following. 



% I understand the mean temperature as that of the whole column of water 

 from top to bottom. 



Am. Jotje. Sci— Thibd Series, Vol. XXXI, No. 183.— March, 1886. 

 11 



