ÖÖI 8x 3 ^c- 0 - Acehbooks.org

S U M A T R A . 3*
except at particular periods, are very unfrequent in the Indian Seas;
where the navigation is well known to be remarkably fafe ; whilft the
furfs are almoft continual; and that gales- are not found to produce this
effect in other extenfive oceans. The weft coaft of Ireland borders a
fea, nearly as extenfive, and much more wild, than the coaft of Sumatra,
and yet there; though when it blows hard, the fvvell on the fliore
is high and dangerous; is there nothing that refembles the furfs of
India.
Thefe, fo general in the tropical latitudes, are, upon the molt pro- Probable caufe
bable hypothefis I have been able to form, after long obfervation, and
much thought and enquiry, the confequence of the trade or perpetual
winds which pervail, at a diftance from fliore, between the parallels cf
ten and thirty degrees north and fouth, whofe uniform and invariable
action caufes a long and conftant fvvell, that exifts even in the calmeft
weather, about the line, towards which its direction tends from either
fide. This fwell or libration of the fea, is fo prodigioufly long, and the
fenfible effect of its height of courfe fo much diminiflied, that it is not
often attended to ; the gradual flope engroffing almoft the whole horizonj
to an eye not very much elevated above its furface: but perfons who
have failed in thofe parts may recollect that even when the fea is apparently
the moft ftill and level, a boat or other object at a diftance from
the fhip, will be hid from the fight of one looking towards it from the
lower deck, for the fpace of minutes together. This fwell, when a
fquall happens, or the wind tremens up, will, for the time, have other
fubfidiary waves on the extent of its] furface, breaking often in a
direction contrary to it, and which will again fubfide as a calm returns,
without having produced on it any perceptible effect. Sumatra, though
not directly expofed to the fouth eaft trade, is not fo diftant but that its
influence may be prefumed to extend to it, and accordingly at Pcok
Pifang near the fouthern extremity of the ifland, a conftant foutherly
fea is obferved, even after a hard northweft wind. This inceflant and
powerful fwell rolling in from an ocean, open even to the pole, fèems
an agent adequate to the prodigious effects produced on the coaft;
whilft •