On the general Causes of the Ocean-Cukrents. 49 



under-current in the Atlantic, another though of subordinate importance 

 and more local operation, viz: the Gulf-stream's mechanical reaction. 



This combination of the streams with each other is facilitated by 

 a cause, which has been by some asserted to l-.e the only cause of the 

 surface-stream's conversion into under-streams, viz: the relations of tem- 

 perature. The salter water of the Gulf-stream ought namely, after being- 

 cooled in the higher latitudes, to sink down below the polar currents 

 fresher water, and this latter, as being colder, should sink below that of 

 the Gulf-stream in the places, where that stream retains a higher tem- 

 perature. If now the ascending warm stream attaches itself as a rection- 

 stream to the descending cold current, it ought somewhere or other in 

 the Polar regions to rise again to the surface, whereby it is chiefly di- 

 luted and cooled by the melting of ice. The in my opinion not impro- 

 bable theory of an open Polar sea has, as in known, been based upon 

 such a reappearance of the warm stream. With the great descending 

 mider-current, caused by evaporation and rainfall, and to the formation 

 of which the trade-winds may also contribute, we need not suppose any 

 separate stream to unite itself, for it is dependent on a disturbed ecjui- 

 librium throughout the whole mass of the ocean. It seems however 

 probable that the cold descending surface-stream in a great measure 

 loses itself in it; if it should be connected with any vertical circulation 

 of great extent, taking place within the Polar tracts, we may find a cause 

 for this in the concentration of the water by the formation of ice at the 

 times and places, when and where that process takes place. But our 

 knowledge of the water's motion in these regions is in fact to limited, 

 to warrant any general conclusions relative to its causes. 



The special object of this work has not been to explain certain 

 particular ocean-streams, but rather to seek out the causes, in which 

 ocean-currents in general originate. But an important touchstone for 

 the correctness of a theory is the trial, whether the phœnomena, actually 

 presented by nature, can by it be explained in a clear and satisfactory 

 maimer. It was therefore especially with respect to reaction-streams de- 

 sirable to endeavour to apply the theory to some particular case, where 

 the circumstances, which may give rise to such streams, seem to be pre- 

 sent in abundance. The explanation of the currents in the Scandinavian 

 waters and in the Strait of Gibraltar would thus be a secondary result 

 consequent to the proving of the theory's applicability. For the same 

 reason it appeared to me desirable to inquire, at what conclusions, with 



Nova Acta Reg. Soc. Sc. Ups. Ser. III. 7 



