THE ARRIVAL OF MAN IN EUROPE 



earth's orbit from the circular form has been 

 exceptionally small. 



Now let us suppose one of these long periods 

 of high eccentricity to coincide with one of the 

 short periods of 10,500 years, when the north- 

 ern hemisphere has its aphelion in winter ; and 

 this, of course, has happened not once only, 

 but a great many times. Under such circum- 

 stances, the northern hemisphere is 98,000,000 

 miles distant from the sun at midwinter instead 

 of 9 1 ,000,000, as at present, and the winter is 

 twenty-six days longer than the summer instead 

 of eight days shorter, as at present. On the 

 other hand, at midsummer the sun's distance is 

 only 86,000,000 miles instead of 94,000,000, 

 as at present. Now how must this state of 

 things affect the climate of the northern hemi- 

 sphere ? 



In the first place, the diminution in the 

 quantity of heat received daily from the sun in 

 winter would be such as to lower the average 

 temperature of the whole northern hemisphere 

 by about 35 F., so that for example the aver- 

 age January temperature of England, which is 

 now 39, would fall to 4. And, conversely, 

 heat enough would be received to raise the 

 mean summer temperature by about 60 above 

 what it now is. 



So far very good, as concerns the amount of 

 heat actually received from the sun. But would 

 5' 



