Introduction: Seasons and Winds. 
19 
to blow towards the parts of the Indian Ocean and islands about the equator, 
now no longer the hottest quarter, stops, and, turning back, commences to move 
towards the heated Continent as the S.W. Monsoon. This wind is general 
from about April to October in the Indian Ocean and the East Indian 
Archipelago north of the equator, sometimes extending as far east as the 
Marianne Islands and as far north as the south of Japan. 
The South-east Monsoon. — During the time that the sun continues north 
of the equator and the South-west Monsoon is blowing, the S.E. Trade-wind 
in general has free course in the Southern Tropics, and from April to October 
is the wind of the East Indian Archipelago south of the equator, 
where it is commonly spoken of as the South-east Monsoon. The general 
direction of it and of the S.W. Monsoon of the Northern East Indies is shown 
on Map III. 
The North-east Monsoon. — When the sun, at the autumnal equinox, passes 
into the southern hemisphere, the N.E. Trade-wind reasserts itself in the parts 
where it has had to give way to the S.W. Monsoon, and, displacing that wind, 
it blows from some time in October, to April. It is then the prevailing 
wind of the Archipelago north of the equator. 
The North-west Monsoon. — At this time of the year, in the zone of calms 
about the equator between the N.E. and S.E. Trade-winds, a westerly monsoon, 
unaccountable to meteorologists at the time of Maury’s celebrated work (1869), 
sets off and blows in a narrow, curved belt across nearly the whole width of 
the great oceans; much, one may suppose, as the return current flows back 
towards the buttresses of the bridge under which a swift river passes. Out of 
this belt there arises the N.W. Monsoon of Australia and the East Indies south 
of the equator. Corresponding with the S.W. Monsoon of the north of the 
equator, the N.W. Monsoon evidently is originated by the heating of the interior 
of Australia and New Guinea during the southern summer, and it is the 
prevailing wind throughout the Archipelago from the equator south- 
wards during the period October to April. See Map IV. 
The Rains: north of the equator. — Between April and October the S W. 
Monsoon, arising in the Indian Ocean about the equator or to the south of it near 
Sumatra, reaches the northern half of that island saturated with moisture and 
produces the rainy season there and along the west coast of the Malay Penin- 
sula. The mountain-ranges running through the middle of that peninsula 
probably hold back the clouds, for, as the wind passes over the east coast, it 
is the fine season there, though there are occasional showers. In the Gulf of 
Siam the wind again commences to take up moisture; here, during the cruise of 
H. M. S. “Saracen” between 1855 — 58 a rough sea was experienced at this time 
of year, and, on the opposite coast “strong breezes with much rain and occasion- 
ally a fresh gale” (Direct. Ind. Arch. 1870 p. 17). Cambodia and the neighbouring 
parts of Siam have then their wet season. Further east the wind, passing over 
the middle of Sumatra and gathering vapour afresh in the south part of the 
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