CROLUS ''CLIMATE AND TIME.'' 819 



demonstrated — no such deflection of the Atlantic current wouki be 

 likely to occur. This possibility is fairly confronted by Dr. Croll 

 when he admits that the gravitation theory " militates strongly " 

 against his theory of secular changes of climate. But there is another 

 self-evident proposition which seems to have escaped his attention. 

 Assuming that the results detailed above follow in the order laid 

 down when the eccentricity is at a high value, it is perfectly manifest 

 that the deflection of the Gulf-Stream feeder is an effect of glaciation, 

 and, if a cause at all, only a secondary one. Hence, if the purely physi- 

 cal agencies alone are capable of causing glaciation. Dr. Croll's theory 

 of secular changes in climate will stand, whether or not the wind theory 

 of oceanic circulation is correct ; but, if they are not capable of pro- 

 ducing a glacial period alone, the theory will fall, even if the wind 

 theory of oceanic circulation be correct. This can not be too strongly 

 emphasized. Yet, not only in " Climate and Time," but in his other 

 publications on the subject, Dr. Croll dwells upon the deflection -of 

 ocean-currents as the principal telluric element in his theory ! 



The only positive evidence adduced to prove that the Gulf Stream 

 was deflected during the glacial period is the fact, pointed out by Mr. 

 Crosskey, that there is more difference between the glacial and recent 

 shells of Scotland than between the glacial and recent shells of Cana- 

 da. But this only proves that the present temperature of that part 

 of Canada is lower than that of Scotland ; for the temperature of the 

 waters at the edge of the ice-sheet must have been approximately the 

 same, whatever the latitude to which it extended. This evidence is, 

 therefore, utterly valueless. Furthermore, we have pretty reliable posi- 

 tive evidence that the Gulf Stream was not stopped during the glacial 

 epoch, in the more northerly limits of continental glaciation in those 

 parts of Europe so greatly affected by the Gulf Stream to-day, any more 

 than in the United States, where its influence is comparatively unfelt. 

 Moreover, Professor Dana has shown in his " Journal " that the distri- 

 bution of ice during the glacial period coincided in a general way with 

 the present distribution of . rainfall in the same latitudes. Now, the 

 greater part of the moisture of the United States, especially of the 

 great Mississippi Basin, is derived from the Gulf o^ Mexico ; and the 

 stoppage of the South Atlantic feeder of the Gulf Stream M'ould 

 cool the waters of the Gulf so considerably as to materially diminish 

 our vapor-supply, and at the same time the distribution would be 

 altered. Similarly, the stoppage of that current during the glacial 

 period would have so altered the distribution that its relation to the 

 present precipitation would not be recognizable, even if it did not so 

 completely cut off the vapor-supply as to prevent glaciation. The 

 mass of evidence is therefore against the hypothesis of the shifting of 

 this important marine current during the glacial period ; and, as this 

 would, as Dr. Croll points out, be likely to be the first out of all of the 

 ocean-cun-ents to be deflected, it may reasonably be doubted whether 



