66 THE PROBLEMS OF THE DEEP SEA n 



upon this complicated problem ; but I may take 

 occasion to remark that the cause of a much 

 simpler phenomenon the stream of Atlantic 

 water which sets through the Straits of Gibraltar, 

 eastward, at the rate of two or three miles an hour 

 or more, does not seem to be so clearly made out 

 as is desirable. 



The facts appear to be that the water of the 

 Mediterranean is very slightly denser than that of 

 the Atlantic (1-0278 to 1-0265), and that the deep 

 water of the Mediterranean is slightly denser than 

 that of the surface ; while the deep water of the 

 Atlantic is, if anything, lighter than that of the 

 surface. Moreover, while a rapid superficial cur- 

 rent is setting in (always, save in exceptionally 

 violent easterly winds) through the Straits of 

 Gibraltar, from the Atlantic to the Mediterranean, 

 a deep undercurrent (together with variable side 

 currents) is setting out through the Straits, from 

 the Mediterranean to the Atlantic. 



Dr. Carpenter adopts, without hesitation, the 

 view that the cause of this indraught of Atlantic 

 water is to be sought in the much more rapid 

 evaporation which takes place from the surface of 

 the Mediterranean than from that of the Atlantic ; 

 and thus, by lowering the level of the former, gives 

 rise to an indraught from the latter. 



But is there any sound foundation for the three 

 assumptions involved here? Firstly, that the 

 evaporation from the Mediterranean, as a whole, 



