ÖÖI 8x 3 ^c- 0 - Acehbooks.org

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S U M A T R A .
center being intenfe, a violent current of air may be perceived to force
its way in, through doors or crevices, on oppofite fides of the houfe.
As the general winds are caufed by the direiï influence of the fun's
rays upon the atmofphere, that particular deviation of the current, diftinguilhed
by the name of land and fea breezes, is caufed by the influence
of his refljfied rays, returned from the earth or fea on which
they ftrike. The furface of the earth is more fuddenly heated by the
rays of the fun, than that of the fea, from its greater denfity and ftate of
reft; confequently it reflects thofe rays fooner and with more power :
but owing alfo to its denfity, the heat is more fuperficial than that imbibed
by the fea, which gets more intimately warmed, by its tranfparency,
and by its motion, continually prefenting a frefh furface to the
fun. I fhall now endeavour to apply thefe principles. By the time the
rifing fun has afcended to the height of thirty or forty degrees above
the horizon, the earth has acquired, and reflected on the body of air
fituated over it, a degree of heat fufficient to rarefy it and deftroy its
equilibrium; in conlequence of which, the body of air above the fea,
not being equally, or fcarce at all rarefied, rufhes towards the land ; and
the fame caufes operating fo long as the fun continues above the horizon,
a conftant fea breeze, or current of air from fea to land, prevails during
that time. From about an hour before fun fet, the furface of the earth,
begins to lofe faft the heat it has acquired from the more perpendicular
rays. That influence of courfe ceafes, and a calm fucceeds. The warmth
imparted to the fea, not fo violent as that of the land, but more deeply
imbibed, and confequently more permanent, now acts in turn, and by
the rarefaction it caufes, draws towards its region, the land air,, grown
cooler, more denfe and heavy, which continues thus to flow back, till
the earth, by a renovation of its heat in the morning, once more obtains
the afcendancy. Such is the general rule, conformable with experience,
and founded, as kfeemsto me, in the laws of motion, and the nature of
things. The following obfervations will ferve to corroborate what I
have advanced, and to throw additional light on the fubject, for the information
and guidance of any future inveftigator. *
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