On the general Causes of the Ocean-Cukrents. 25 



itself this increase augments in rapid progression, so that e. g. 100 vo- 

 lumes of river-water, at 6000 foots distance outside the mouth of the 

 river, will according to the same calculation have grown to 552 volumes. 

 That the velocity of the stream cannot decrease in the same progres- 

 sion, in which the volumes increase, I have before endeavoured to show; 

 the figures here adduced can therefore give an idea, although imperfect, 

 how much larger the stream is, which a river produces in the sea, than 

 the original river itself. The examination of the velocity of the stream 

 at different depths, etc., necessary for the complete discussion of the 

 ({uestion, circumstances however did not allow me to undertake. 



If the under-current here described were caused by differences of 

 pressure, dependent on the difference of specific gravity between sea- and 

 river-water, those differences of pressure would necessarily be very con- 

 siderable, for they would have to drive the sea-water at least 12000 

 Mètres from the Kattegat to the mouth of the river, and when there to 

 raise it from the lower to the higher level, press it in through the 

 mouth of the river, and then drive it 5 or 6 Kilomètres up the bed of 

 the river, in doing which it would have to overcome both the friction 

 against the bottom and that of the powerful outflowing stream of the 

 river. If we now cast our eyes on the table of the specific weights ob- 

 served, we find, that, as regards the strata of water between the bottom 

 and 2 fathoms depth under the surface, the specific weight of such a 

 column of water, taken anywhere whatever, will be equal to or greater 

 than the specific weight of an equally high column, taken at the station 

 farthest out from land '). In order to account for the under-current we 

 have als(^ nothing left, but the difference of specific weight, which the 

 pillars of fluid above the depth of 2 fathoms under the surface exhibit. 

 If then we assume for the pillar farthest out to sea a specific weight of 

 l.Oiiill, such as I observed in the Kattegat at Wiuga, and for the oppo- 

 site side a specific weight of 1.000, the difierence of pressure for a height 

 of 2 fathoms will correspond to the pressure of 6 centimètres of pure 

 water, which pressure would be attained only when the two extremities 

 of the space were on the same level. But this last condition is impos- 

 sible, for the tolerably strong stream of the river presupposes a certain 

 inclination of its surface. In order that the level of the river at the 



') I may add that at that season of the year one does not in the Kattegat, 

 outside the opening of the fjord, meet with sensibly heavier water, than at correspon- 

 ding depth near the river-mouth. 



Nova Acta Reg, Soc. Sc. Ups. Ser. III- 4 



