CHAPTER IV. 



OBJECTION THAT THE AIR AT THE EQUATOR IS NOT 

 HOTTER IN JANUARY THAN IN JULY. 



Influence of the present distribution of Land and Water. — The 

 Summer of the Southern Hemisphere colder than that of the 

 Northern. — Influence of the Trade Winds on the Temperature 

 of the Equator. 



The fact that the temperature of the equator in 

 January, when the earth is in perihelion, is not higher 

 than in July, when in aphelion, has been urged as an 

 objection to the Physical Theory. When we examine, 

 however, the reason of this apparently curious circum- 

 stance, we find that there is certainly no real grounds 

 for the objection. 



The temperature referred to is, of course, the 

 ordinary temperature as indicated by the shade 

 thermometer, which is simply that of the air. The 

 objection is more apparent than real ; for if we 

 examine the indirect results which follow from the 

 present distribution of land and water, we shall see 

 that there is no reason whatever why the air at the 

 equator should be hotter in January than in July. 



It is well known that, notwithstanding the nearness 

 of the sun in January, the influence of the present 

 distribution of land and water is sufficient to make 

 the mean temperature of the whole earth, or, what is 

 the same, the mean temperature of the air over the 

 surface of the earth higher in July than in January. 



