1 CLIMATE AND ASPECTS OF THE EQUATORIAL ZONE 221 
places, 90° Fahr. being sometimes reached with us and not 
being often very much exceeded at Batavia. 
Causes of the uniform High Temperature near the Equator 
It is popularly supposed that the uniform high temperature 
of the tropics is sufficiently explained by the greater altitude, 
and therefore greater heating-power of the midday sun; but 
a little consideration will show that this alone by no means 
accounts for the phenomenon. The island of Java is situated 
in from six and a half to eight and a half degrees of south 
latitude, and in the month of June the sun’s altitude at noon 
will not be more than from 58° to 60°. In the same month 
at London, which is fifty-one and a half degrees of north 
latitude, the sun’s noonday altitude is 62°. But besides this 
difference of altitude in favour of London there is a still more 
important difference, for in Java the day is only about eleven 
and a half hours long in the month of June, while at London 
it is sixteen hours long, so that the total amount of sun-heat 
received by the earth must be then very much greater at 
London than at Batavia. Yet at the former place the mean 
temperature of the day and night is under 60° Fahr., while 
in the latter place it is 80° Fahr., the daily maximum being 
on the average in the one case about 68° and in the other 
about 89°. 
Neither does the temperature at the same place depend 
upon the height of the sun at noon ; for at Batavia it is nearly 
vertical during October and February, but these are far from 
being the hottest months, which are May, June, and Sep- 
tember, while December, January, and February are the 
coldest months, although then the sun attains nearly its 
greatest altitude. It is evident, therefore, that a difference of 
30° in the altitude of the sun at noon, at different times of 
the year, has no apparent influence in raising the temperature 
of a place near the equator, and hence we conclude that other 
agencies are at work which often completely neutralise the 
effect. which increased altitude must undoubtedly exert. 
There is another important difference between the tem- 
perate and tropical zones, in the direct heating effect of the 
sun’s rays independently of altitude. In England the noon- 
day sun in the month of June rarely inconveniences us or 
