356 Notices of Books. [July, 
winds as a cause for the existing currents of the ocean. He 
said, ‘‘ ‘ Theoretically considered, it appears plausible enough to 
assume that the winds must tend, to some extent, to cause a system 
of currents, by driving the surface water before them; which, 
wherever it accumulates against obstructions, must tend to run 
off in streams. But, practically considered—that is to say, 
considering what are the actual winds which blow, and what the 
actual currents of the ocean—it appears to us incomprehensible 
how any one who studies these systems of aérial and oceanic 
circulation can reconcile them as cause and effect. It appears 
to us surprising how, considering the enormous volume and 
weight of water borne along in the oceanic currents, any one 
can help doubting the power of the comparatively light 
atmosphere to keep such a mass in motion, even if it were 
shown that the course of the oceanic currents corresponded 
with that which would naturally result from the action of the 
winds which exist. But when it is found that the winds tend to 
a great extent to neutralise each other, and that, even in the 
region of the Trade Winds, where the power of the winds is 
greatest, ocean currents, even on the surface of the ocean, run 
across and against those winds, whilst in the lower strata 
immense under-currents run their course regardless of the winds 
which blow above; it then seems surprising how any one can 
consider that the position and direction of the ocean currents 
which exist are in accordance with the current-creating action of 
the winds, even if it be assumed that the latter are sufficiently 
powerful to control the enormous volume of water which is 
carried along in those currents.’”* 
He also endeavoured to show the inefficiency of the Tempe- 
rature theory. And after making use of Sir John- Herschel’s 
arguments, said: ‘‘‘ Besides the objections urged by Sir John 
Herschel against the theory which makes differences in specific 
gravity the prime cause of the currents of the ocean, we may 
here observe that, if differences in specific gravity, resulting 
from the difference of temperature and other conditions in Polar 
and Equatorial regions, were the principal cause of ocean 
currents—in consequence of the tendency of the heated and 
cold water to exchange positions in order to re-establish their 
equilibrium in specific gravity—then the heated water flowing 
from the Equator would be under that influence of change of 
latitude which tends to carry it eastwards, and the cold water 
from the Polar regions would be under that influence of change 
of latitude which tends to carry it westwards; so that, therefore, 
the warm water would naturally flow from the Equator on the 
east side of the ocean, and the cold water as naturally flow 
towards the Equator on the west side of the ocean; whereas, in 
fact, with the actually existing currents of the ocean, the very 
* Vis-Inertiz, p. 62. London: Longmans, 1868. 
