S. Newcomh—Grolts Climate and Time. 265 



render it worthy of very careful considei-ation, although, owing 

 to the dififuse mode of treatment adopted, the complete mastery 

 of his views is a very difficult task. For this reason it is not 

 easy for the reviewer to feel sure that he is giving such a state- 

 ment of the author's views as the author himself would regard 

 as entirely satisfactory. We may say, however, in brief, that 

 one great object of the author is to insist upon the important 

 agencies played by ocean currents in influencing climate. In- 

 deed, beyond the regular astronomical variation of climate 

 with the latitude, this seems to be the only influence which he 

 will allow to be important. The influence of the Gulf Stream 

 in modifying the climate of Northeastern Europe receives es- 

 pecial attention, and his views of this influence seem quite 

 well grounded. We had supposed the view that the warm and 

 equable climate of that region was due to the Gulf Stream to 

 be one universally held, although no one had attempted to ren- 

 der it plausible by an actual calculation of the amount of heat 

 conveyed by that stream. This calculation Mr. Croll has 

 made, and having reduced his own estimate of the volume of 

 the stream to one-half, in deference to the views of some of his 

 opponents, he shows that the amount of heat annually con- 

 veyed away by the stream is equal to the whole amount which 

 a belt of the earth sixty-four miles broad, extending all round 

 the equator, receives from the sun. We make the quantity a lit- 

 tle less, but yet equivalent to more than the total amount of heat 

 which falls on a million of square miles at the equator. Mak- 

 ing all allowance for the uncertainties of these data, and for 

 the fact that only one of the two branches of the Gulf Stream 

 passes over to Northeastern Europe, it must yet be admitted 

 that the quantity of heat which that region receives from the 

 Gulf Stream is not an inconsiderable fraction of that which it 

 receives from the sun. 



An essential part of Mr. Croll's system is the wind theory of 

 oceanic circulation, essential, however, to his views of the cli- 

 mate of the glacial period rather than to the climate of the 

 present. This is a point on which there is some difference be- 

 tween Mr. Croll and his numerous opponents, especially Dr. 

 Carpenter. Having made no examination of the views of Dr. 

 Carpenter, we cannot pronounce them wrong, but the view 

 maintained by Mr. Croll, that the winds are the principal 

 causes of ocean currents seems well sustained. The direction of 

 these currents may be materially modified by the earth's rota- 

 tion, a cause which can be investigated only by mathematical 

 methods, and until the mode of operation of this cause is fully 

 understood, we cannot feel sure that the theory is complete. 

 So far as we are aware Mr. Ferrel is the only mathematician 

 who has entered upon this investigation, but Mr. Croll does not 

 seem to have made much use of his results. The principal 



