316 MAN AND THE GLACIAL PERIOD. 



no means so hot now as, theoretically, it ought to be, and 

 that the arctic regions are not so cold as, according to 

 theory, they should be, and this in places which could not 

 be affected by oceanic currents. For example, at Iquitos, 

 on the Amazon, only three hundred feet above tide, three 

 degrees and a half south of the equator, and more than a 

 thousand miles from the Atlantic (so that ocean-currents 

 cannot abstract the heat from its vicinity), the mean 

 yearly temperature is but 78° Fahr. ; while at Verkhojansk, 

 in northeast Siberia, which is 67° north of the equator, 

 and is situated where it is out of the reach of ocean- cur- 

 rents, and where the conditions for the radiation of heat 

 are most favourable, and where, indeed, the winter is the 

 coldest on the globe (January averaging — 56° Fahr.), the 

 mean yearly temperature is two degrees and a half above 

 zero ; so that the difference between the temperature upon 

 the equator and that at the coldest point on the sixty- 

 seventh parallel is only about 75° Fahr. ; whereas, if tem- 

 perature were in proportion to heat received from the sun, 

 the difference ought to be 172°. Again, the difference 

 between the actual January temperature on the fiftieth 

 parallel and that upon the sixtieth is but 20° Fahr., 

 whereas, the quantity of solar heat received on the fiftieth 

 parallel during the month of January is three times that 

 received upon the sixtieth, and the difference in tempera- 

 ture ought to be about 170° Fahr. upon any known law 

 in the case. 



Woeikoff, a Eussian meteorologist, and one of the 

 ablest critics of Mr. Croll's theory, and to whom we are 

 indebted for these facts, ascribes the greater present 

 warmth of the northern Atlantic basin, not to the astro- 

 nomical cause invoked by Mr. Croll, but to the relatively 

 small extent of sea in the middle latitudes of the northern 

 hemisphere. The extent and depth of the oceans of the 

 southern hemisphere would of themselves give greater 

 steadiness and force to its trade-winds, and lead to a gen- 



