68 THE PROBLEMS OF THE DEEP SEA n 



Again, if the Gibraltar indraught is the effect of 

 evaporation, why does it go on in winter as well 

 as in summer ? 



All these are questions more easily asked than 

 answered ; but they must be answered before we 

 can accept the Gibraltar stream as an example 

 of a current produced by indraught with any 

 comfort. 



The Mediterranean is not included in the 

 Challenger 's route, but she will visit one of the 

 most promising and little explored of hydro- 

 graphical regions the North Pacific, between 

 Polynesia and the Asiatic and American shores ; 

 and doubtless the store of observations upon the 

 currents of this region, which she will accumulate, 

 when compared with what we know of the North 

 Atlantic, will throw a powerful light upon the 

 present obscurity of the Gulf-stream problem. 



