On the general Causes of the Ocean-Currents. 27 



present, as compared with ordinary river mouths, will then be the follo- 

 wing. The under-current, which enters an ordinary river-mouth, meets a 

 gradually diminishing depth; that, which enters the mouth of a channel, 

 such as we are considering, soon arrives at a gradually increasing one. 

 The stream therefore sinks to the bottom of the basin, fills its hollows, 

 overflows its bars, whereby the water, that had previously lain at the 

 bottom, is raised nearer to the surface. This water, thus raised to a 

 level of greater extent, which was previously covered with still lighter 

 water, diffuses itself there, and moreover is sucked to the borders and 

 innermost branches of the basin by the reaction-streams, which the rivers 

 produce at their embouchures. At these last spots the deep water rises 

 most rapidly towards the surface, after having passed through many 

 degrees of dilutation, and returns, mixed with river-water, to the ocean. 

 The cause, which gives rise to all these motions is, in my opinion, to 

 be looked for in the vis viva to be found partly in the superficial stream 

 at the mouth of the basin, and partly in the much slower flow on the 

 large surface of the basin, and lastly in the more rapid upper-streams 

 in the vicinity of the river-mouths. 



There is perhaps no branch of the ocean, where these streams 

 have been developed in so copious and various a manner, as in the sy- 

 stem of waters, that surrounds the coasts of Sweden. I proceed there- 

 fore, for the further illustration of the subiect, to communicate the prin- 

 cipal features of the water-circulation within that system, as far as it is, 

 chiefly through my own researches, known to me. This system is, as 

 is generally known, composed of a series of larger and smaller ocean- 

 basins, separated from each other by promontories and island groups, 

 which penetrates into the land in many sinuosities from the southermost 

 point of Norway till Torneå, a distance in all of 1200 Engl, sea-miles. 

 These different basins, each of which has its own hydrographical charac- 

 ter, are the Skagerack and Kattegat^ the mutual limit of which is the 

 Skaw point, the western branches of the Baltic between Bornholm, Eugen 

 and the Danish isles, the Baltic itself between Bornholm and the Åland 

 group of isles, the Bothnia?! sea between the Aland isles and the con- 

 traction of the gulf called Qvarken, and lastly the gulf of Bothnia, the 

 most northerly. The smallest channel of communication between these 

 is that, which unites the Kattegat and the western branches of the Bal- 

 tic. There, in the many straits between the Danish islands, the abun- 

 dance of river-water, which the three last divisions receive, as also the 

 under-current towards the Baltic must penetrate, and that under-current 



