374 THE DEPTHS OF THE SEA. (CHAP. VIII. 
accepted. Dr. Carpenter believes, however, that the 
conditions in the Strait of Gibraltar and in the 
Baltic Sound aptly illustrate the general circulation 
in the ocean, and confirm his views. 
I quote from the general summary of Dr. Car- 
penter’s address to the Geographical Society :— 
“The application of the foregoing principles to 
the particular cases discussed in the paper is as 
follows :— 
« VITI.—A vertical circulation is maintained in 
the Strait of Gibraltar by the excess of evaporation 
in the Mediterranean over the amount of fresh water 
returned into its basin, which at the same time 
lowers its level and increases its density; so that 
the surface inflow of salt water which restores its 
level (exceeding by the weight of salt contained 
in it the weight of fresh water which has passed off 
by evaporation) disturbs the equilibrium and pro- 
duces a deep outflow, which in its turn lowers the 
level. The same may be assumed to be the case 
in the Strait of Babelmandeb. 
“TX.—A vertical circulation is maintained in the 
Baltic Sound by an excess in the influx of fresh 
water into the Baltic; which at the same time 
raises its level and diminishes its density, so as to 
produce a surface outflow, leaving the Baltic column 
the lighter of the two, so that a deep inflow must 
take place to restore the equilibrium. The same 
may be assumed to be the case in the Bosphorus 
and Dardanelles. 
“ X.—A vertical circulation must, on the same 
principles, be maintained between polar and equa- 
torial waters by the difference of their temperatures : 
