Jl SUM A T R A. 
whilfl: its very fize contribiites to its being overlooked. It reconcUcs 
almoft all tbe difficulties which the phoeaomena feem to piefeat, and in 
particular it accounts for »the decreafe of the furf during the N. W, 
monfoon^ the local wind then counteracting the operation of the general 
one ; and it is corroborated by an obfervation I have made, that the 
furfs on the Sunaatran coaft ever begin to break at their Ibuthern extreme, 
the motion of the fwell not being perpendicular te the dtre^Hon of the 
fhorc. This manner of explaining their origin feems to carry much 
reafon with it, but there occurs to me one obje«flion which I cannot get 
over, and which a regard to truth obliges me to date. The trade winds 
are remarkably ftcady and uQiform, and the fwell generated by them is 
the fame. The furfs are much the reverfe, feldom perfcvering for two 
days in the fame degree of violence; often mountains h^gh in the 
morning, ana ncany muaaea oy nignr, Wow comes an uniform eaufe to 
produce effeds fo unfteady; unlefs by the intervention of fecondary 
-cauies whofe nature and operation we are unacquainted with } 
It is clear to me that the furfs, as above defcribed, are peculiar to 
thofe climates which lie within the remoter limits of the trade winds, 
though in higher latitudes, large fwells and irregular breakings of 
the fea are to be met with, after boifterous weather. Poflibly the fol- 
lowing caufes may be judged to confpire, with that I have already fpe- 
cified, towards occafioning this diilin^tion. The former region being 
expofed to the immediate inflluence of the two great lumii^aiies, the 
water, fmm thAr filr^A iiauic to more violent agitation, 
than nearer the poles, where their power is felt only by indirect com- 
munication. The equatorial parts of the earth performing their diur- 
nal revolution wiih greater velocity than the refl, a larger circle being 
defcribed in the fame time, the waters thereabout, from the ftronger 
centrifugal force, may be fuppofed more buoyant; to feel lefs reftraint 
from tlie fluggifli principle of matter ; to have lefs gravity; and there- 
fore £0 be more obedient to external impulfes of everj' kind, whether 
from the winds or ^ny other caufc. 
The 
