354 Notices of Books. (July, 
other fact is, that if water were set in motion between the 
Equator and the Poles by differences of temperature, the rotation 
of the earth would immediately act upon it, tending to carry 
that moving towards the Equator westwards, and that moving 
towards the Poles eastwards; so that one of the most striking 
features of the circulation would be the tendency of the cold 
water to flow towards the Equator on the west of the ocean, 
eastwards through the equatorial regions, and to branch off 
northwards and southwards as warm currents, on the east of the 
ocean. These general features are exactly the reverse of the 
general features of the circulation which actually exists; and 
therefore nothing more is requisite to explode the theory; for 
what must be the result when fact and theory clash like this? 
‘‘ Besides this broad discordance with actual facts, the details 
of Dr. Carpenter’s theory are open to criticism. Is not the 
assertion, that a difference of level in the ocean will cause a 
surface current, rather reckless? Has it been certified by ex- 
perience? or can any recorded phenomena be adduced in support 
of it?” 
The system of upper and under currents through the Strait of 
Gibraltar and the Sound, Mr. Jordan goes on to show to be the 
“result of differences in specific gravity, as explained by Captain 
Maury’s theory, which had better be left in its original simplicity, 
for this modification, with which Dr. Carpenter has attempted 
to encumber it, is not an improvement, but an erroneous com- 
plication.” 
‘‘Captain Maury says wherever there is a ‘difference of 
specific gravity between sea-water at one place and sea-water at 
another,’ ‘whether it be owing to difference of temperature or to 
difference of saltness, &c., it is a difference that disturbs 
equilibrium, and currents are the consequence. The heavier 
water goes towards the lighter, and the lighter whence the heavier 
comes; for two fluids differing in specific gravity, and standing 
at the same level, can no more balance each other than unequal 
weights in opposite scales of a true balance. It is immaterial 
whether this difference of specific gravity be caused by tem- 
perature, by the matter held in solution, or by any other thing; 
the effect is the same, namely, a current.’* This is sufficient to 
account for the Gibraltar current without the necessity of a 
surface current caused by difference of level, to set the cir- 
culation in motion. The Atlantic water which supplies the waste 
caused by evaporation in the Mediterranean flows in as a surface 
current because it is lighter than that of the latter sea, which the 
action of specific gravity consequently carries out below it. 
‘‘ The currents in the Experimental Illustration of the General 
Oceanic Circulation in which water in a long narrow trough, as 
exhibited before the Royal Geographical Society, is heated at 
the surface of one end by a lamp and chilled at the other by ice, 
* Physical Geography of the Sea, par. 406. 
