UNIFORMITY OF CLIMATE. 17 



portion of the tropical and subtropical zones where the 

 trade-winds constantly blow, as the evaporation must 

 there be enormous while the quantity of rain is very 

 small. It follows, then, that on the equatorial land- 

 surface there will be a considerable balance of conden- 

 sation over evaporation which must tend to the general 

 raising of the temperature, and, owing to the conden- 

 sation being principally at night, not less powerfully to 

 its equalisation. 



General Features of the Equatorial Climate. The 

 various causes now enumerated are sufficient to enable 

 us to understand how the great characteristic features 

 of the climate of the equatorial zone are brought about ; 

 how it is that so high a temperature is maintained 

 during the absence of the sun at night, and why so 

 little effect is produced by the sun's varying altitude 

 during its passage from the northern to the southern 

 tropic. In this favoured zone the heat is never oppres- 

 sive, as it so often becomes on the borders of the 

 tropics ; and the large absolute amount of moisture 

 always present in the air, is almost as congenial to the 

 health of man as it is favourable to the growth and 

 development of vegetation. 1 Again, the lowering of 

 the temperature at night is so regular and yet so strictly 

 limited in amount, that, although never cold enough to 

 be unpleasant, the nights are never so oppressively hot 

 as to prevent sleep. During the wettest months of 

 the year, it is rare to have many days in succession 



1 Where the inhabitants adapt their mode of life to the peculiarities of 

 the climate, as is the case with the Dutch in the Malay Archipelago, they 

 enjoy as robust health as in Europe, both in the case of persons born in 

 Europe and of those who for generations have lived under a vertical sun. 



C 



