On the general Causes of the Ocean-Currents. 2 I 



When a river debouches into the sea, these phœnomena have an 

 entirely different character. By the river-water, cast upon the surface, 

 the equilibrium is disturbed only to a certain depth, that is, as soon as 

 the water-strata have arranged themselves as the supply of the river and 

 the dimensions of the creek require. The stream of river-water flowing 

 over the svu-face cannot maintain its original direction. In consequence 

 of the higher level, which accords with its lighter weight, the river- 

 water must diffuse itself towards the sides, while flowing forward. The 

 rivei'-water is thus diffused like a covering over the salt-water, dragging 

 with it everywhere molecules of sea-water, where the surfaces are in 

 contact. The result of the reaction will thus be almost exclusively^ an 

 under-current, commencing in the open sea and pursuing its way under 

 the broad upper-current of fresher water to the mouth of the river; if 

 the depth at the mouth is sufficient, the under-current will penetrate 

 into the river itself. At the mouths of the rivers, that fall out into 

 arms of the sea of considerable length and gradually narrowing, under- 

 currents of this kind will be most powerful. 



The difference, that exists between the sea and lakes with 

 respect to the streams caused by rivers, is sufficiently explained by 

 what has been said above. There is however one additional circum- 

 stance to be taken into consideration, namely the effect, that the ten- 

 dency to diffusion between fresh and salt water may produce. This 

 seams to be of a double character. In the first place it is clear, that at 

 the moment the streaming river-water diffuses itself in the salt-water, it 

 communicates to the latter its motion without suffering so great a loss 

 of vis viva, as takes place, if the motion is caused exclusively by fric- 

 tion, as in a fresh-water lake. Secondlj^ the diffusion causes a continual 

 change in the hydrostatical equilibrium. If in fact we suppose a stratum 

 of fresh-water to lie upon the sea-water, the level of which with respect 

 to the latter is determined by the specific weight of the water, the limit, 

 where equilibrium prevails, will by the diffusion be brought lower, and 

 at the same time the pressure in the immediately superjacent levels in- 

 creased. The final effect of this on the motion of the water-strata would, 

 I think, be to increase the power of the surface stream, and thus also 

 to strengthen the under-current. 



For fuller illustration of the effect, that river-water has upon the 

 sea, I herewith communicate the principal results of the experiments I 

 made on the 5"' Aug. last year at the mouth of the Göta-Elf at Göte- 



