24 
CAUSES OP 1'IIE CUJLKEJTTS. 
east ; and it would seem that the cause of this phenomenon 
should be sought in the constancy of the westerly winds 
which prevail in the high latitudes. Besides, the particles 
ot water do not move with the same rapidity as the particles 
ot air ; and the currents of the ocean, which we consider as 
most, rapid, have only a swiftness of eight or nine feet a 
second ; it is consequently very probable, that the water 
m passing through different parallels, gradually acquires a 
velocity correspondent to those parallels, and that the 
rotation of the earth does not change the direction of the 
currents. 
The variable pressure on the surface of the sea, caused by 
the changes in the weight of the ah’, is another cause 
ot motion which deserves particular attention. It is well 
known, that the barometric variations do not in general 
take place at the same moment in two distant points, which 
are on the same level. If in one of these points the barome- 
ter stands a few lines lower than in the other, the w ater will 
rise where it finds the least pressure of air, and this local intu- 
mescence will continue, till, from the effect of the wind the 
equilibrium of the air is restored. M. Yaueher thinks 
that the tides in the lake of Geneva, known by the name of 
the scic/ies, arise from the same cause. Wc know not whether 
it ho the same, when the movement of progression, which 
must not he confounded with the oscillation of the waves 
is the effect of an external impulse. if. de Fleuricu, in his 
narrative of the voyage of the Isis, cites several facts’ which 
render it probable that the sea is not so still at the bottom 
as naturalists generally suppose. "Without entering here 
into a discussion of this question, wc shdU only observe that 
i the external impulse is constant in its action, like that of 
the trade-winds, the friction ot the particles of water on each 
other must necessariily propagate the motion of the surface 
ot the ocean even to the lower strata ; and in fact this pro- 
pagation in the Oulf-stream lias long been admitted by 
navigators, who think they discover the effects in the great 
depth of the sea wherever it is traversed by the current of 
Honda, even amidst tho sand-banlcs which surround the 
northern coasts of the United States. This immense river 
of hot waters, after a course of fifty days, from the 24th to 
am 45th degree cf latitude, or 450 leagues, does not lose 
