1872.] 



c Shearwater ' Scientific Researches. 



637 



made into a dining-table for the Governor of Holsteenborg. Moreover it 

 has been noticed by several trustworthy observers, that icebergs often move 

 northwards in Davis's Straits, in opposition to a southerly moving surface- 

 current, as also against the wind. And although it might seem anomalous 

 for a warmer stream to be flowing beneath a colder one, yet the anomaly 

 disappears when we bear in mind that the surface-current, being composed 

 in great degree of water which is the product of the liquefaction of icebergs, 

 may have its salinity so reduced as to be specifically lighter than ordinary 

 Oceanic water of higher temperature (§ 15). Although this warmer 

 north-flowing body of water is assumed by Dr. Miihry to be a branch of 

 the " Gulf-stream," there is a total absence of indication that it is derived 

 from any other source than the general North-Atlantic area. 



163. I come, lastly, to consider the question : — Whether the North- 

 easterly flow of relatively warm water, by which the Climate of the 

 British Islands, and still more that of regions lying within the Arctic 

 circle, is ameliorated, is attributable to the persistence of the initial force 

 of the Gulf-stream proper, supplemented by the general Easterly surface- 

 drift of the North Atlantic ; or ivhether it is a larger and deeper move- 

 ment, forming part of a General Oceanic Circulation sustained by difference 

 of Temperature. — As the direction of the Gulf-stream proper, where it is 

 last to be recognized as a distinct Current, is nearly due East, and as the 

 incidence of the Polar current off Newfoundland on its northern side will 

 tend to give it rather a southward than a northward direction, the sudden 

 northward deflection of the Isothermal lines on the eastern border of the 

 Polar current, and their course of parallelism to the Greenland coast 

 (which is as marked as the parallelism of the Gulf-stream to the coast of 

 the United States as far north as Cape Hatteras), do not seem explicable on 

 the idea of a vis a tergo ; which must not only extend itself over the 

 vast Oceanic area that intervenes between the eastern coast of Greenland 

 and Scandinavia, but must change the direction of its operation without 

 any assignable cause. Still less can it be shown, on this hypothesis, 

 how a branch of the Gulf-stream should actually turn " round the corner " 

 westwards into Baffin's Bay, so as to pass fromW.Long. 50°to"W r .Long. 70°; 

 and this notwithstanding its excess of easterly momentum, which would 

 tend to carry any north-moving stream in the direction of Spitzbergen. 

 Further, when we take account of the retardation which the Gulf-stream 

 is known to undergo when flowing in the early part of its course as a 

 compact and powerful current, it seems scarcely conceivable that it can 

 long retain enough of its initial force to continue to make its way, when 

 superficially extended over so vast a surface, against the retarding in- 

 fluence of the increased friction to which that extension must subject 

 it with the watery bed over which it flows. And though it may be said, 

 in answer to this objection, that its movement will be aided by the 

 prevalent surface-drift, yet the influence of this can only extend to a 

 very small depth ; and the advocates of the " Gulf-stream " doctrine take 



