i CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 225 
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 subtropical 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. 
Q 
