, the periodical winds, or monsoons
as they are termed in the latter, blow from the west-north-west and
south-west, according to the situation, extent, and nature of the nearest
lands; the effect of which upon the incumbent atmosphere, when heated by
the sun at those seasons in which he is vertical, is prodigious, and
possibly superior to that of any other cause which contributes to the
production or direction of wind. To trace the operation of this irregular
principle through the several winds prevalent in India, and their
periodical failures and changes, would prove an intricate but, I
conceive, by no means an impossible task.* It is foreign however to my
present purpose, and I shall only observe that the north-east monsoon is
changed, on the western coast of Sumatra, to north-west or
west-north-west by the influence of the land. During the south-east
monsoon the wind is found to blow there, between that point and south.
Whilst the sun continues near the equator the winds are variable, nor is
their direction fixed till he has advanced several degrees towards the
tropic: and this is the cause of the monsoons usually setting in, as I
have observed, about May and November, instead of the equinoctial months.

(*Footnote. It has been attempted, and with much ingenious reasoning, by
Mr. Semeyns in the third volume of the Haerlem Transactions which have
but lately fallen into my hands.)

LAND AND SEA BREEZES.

Thus much is sufficient with regard to the periodical winds. I shall
proceed to give an account of those distinguished by the appellation of
land and sea breezes, which require from me a minuter investigation, both
because, as being more local, they more especially belong to my subject,
and that their nature has hitherto been less particularly treated of by
naturalists.

In this island, as well as all other countries between the tropics of any
considerable extent, the wind uniformly blows from the sea to the land
for a certain number of hours in the four and twenty, and then changes
and blows for about as many from the land to the sea; excepting only when
the monsoon rages with remarkable violence, and even at such time the
wind rarely fails to incline a few points, in compliance with the efforts
of the subordinate clause, which has not power, under these
circumstances, to produce an entire change. On the west coast of Sumatra
the sea-breeze usually sets in, after an hour or two of calm, about ten
in the forenoon,