i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 226 



tion ; in the other case it radiates away into space, and is lost, 

 more rapidly than it is being absorbed. In both cases an 

 equilibrium will be arrived at, but in the one case the result- 

 ing mean temperature will be much higher than in the other. 

 Thus we can understand the burning effects of the sun's rays 

 in the tropics, since it results from the inability of the skin 

 to part with the heat, either by radiation, evaporation, or 

 absorption, as fast as it is received, and thus a temperature is 

 quickly reached which disorganises the delicate structures of 

 the epidermis. 



Influence of Winds on the Temperature of the Equator 

 The distance from the northern to the southern tropics 

 being considerably more than three thousand miles, and the 

 area of the intertropical zone more than one-third the whole 

 area of the globe, it becomes hardly possible for any currents 

 of air to reach the equatorial belt without being previously 

 warmed by contact with the earth or ocean, or by mixture 

 with the heated surface-air which is found in all intertropical 

 and sub-tropical lands. This warming of the air is rendered 

 more certain and more effective by the circumstance that all 

 currents of air coming from the north or south have their 

 direction changed owing to the increasing rapidity of the 

 earth's rotational velocity, so that they reach the equator as 

 easterly winds, and thus pass obliquely over a great extent of 

 the heated surface of the globe. The causes that produce the 

 westerly monsoons act in a similar manner, so that on the 

 equator direct north or south winds, except as local land and 

 sea-breezes, are almost unknown. The Batavia observations 

 show that for ten months in the year the average direction 

 of the wind varies only between 5 and 30 from due east or 

 west, and these are also the strongest winds. In the two 

 months March and October when the winds are northerly, 

 they are very light, and are probably in great part local 

 sea-breezes, which, from the position of Batavia, must 

 come from the north over about two thousand miles of warm 

 land and sea. As a rule, therefore, every current of air at 

 or near the equator has passed obliquely over an immense 

 extent of tropical surface and is thus necessarily a warm 

 wind. 



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