CHAP. VIIL] THE G ULF-STREAM. 397 



The North Atlantic and Arctic seas form together 

 a cul de sac closed to the northward, for there is 

 practically no passage for a body of water through 

 Behring's Strait. While, therefore, a large portion 

 of the water, finding no free outlet towards the 

 north-east, turns southward at the Azores, the re- 

 mainder, instead of thinning off, has rather a ten- 

 dency to accumulate against the coasts bounding 

 the northern portions of the trough. We accordingly 

 find that it has a depth off the west coast of Iceland 

 of at least 4,800 feet, with an unknown lateral 

 extension. Dr. Carpenter, discussing this opinion, 

 says : " It is to me physically inconceivable that 

 this surface film of lighter (because warmer) water 

 should collect itself together again even supposing 

 it still to retain any excess of temperature and 

 should burrow downwards into the ' trough,' dis- 

 placing colder and heavier water, to a depth much 

 greater than that which it possesses at the point of 

 its greatest e glory' its passage through the Florida 

 Narrows. The upholders of this hypothesis have to 

 explain how such a re-collection and dipping-down 

 of the Gulf-stream water is to be accounted for on 

 physical principles." J I believe that as a rule, 

 experimental imitations on a small scale are of little 

 use in the illustration of natural phenomena ; a very 

 simple experiment will, however, show that such a 

 process is possible. If we put a tablespoonful of 

 cochineal into a can of hot water, so as to give it 

 a red tint, and then run it through a piece of india- 

 rubber tube with a considerable impulse along the 

 surface of a quantity of cold water in a bath, we see 



1 Dr. Carpenter's Address to Geographical Society, op. cit. 



