KUNGL. SV. VET. AKADEMIENS HANDLINGAR. HAND 47. N:<) 4. 39 



current, in the form of what may be termed a submarine solitary wave (»Ubertragunu - 

 welle»), and when the pendulum has been working for a few periods, quite a regular 

 procession of such waves is obtained. (Pl. II & III ). 



Of course, in a liniited tank, these effects cannot go on for ever. As soon as the 

 boundary to the right, on account of the fresh-water sucked out, has sunk so far that even 

 at high-water it is no longer heaved up above the top of the ridge, there will not be any 

 more salt-water passing the barrier. Finally a state of equilibrium is established, the 

 aspect of which (at high-water) is given by Fig. 7. 



There are still boundary-waves formed, but of a smaller amplitude, and they have 

 no influence upon the density distribution of the two compartments. 



The modified arrangement of three layers of water described on p. 35 is of importance 

 as approaching in a manner to the case that, within a certain intermediate stratum, there 

 is a gradual transition of density. This of course generally occurs in Nature. To ob- 

 tain a beautiful experiment, there should^be used a quantity of mixed water just suffi- 

 cient to produce a thin straight line of black, stretching right wards from the top of the 

 barrier. The pendulum being put in action, this line continously agitated by a sinuous 

 motion presents a very striking aspect. (Pl. III: 3 — 6). 



Fig. 7. 



With reference to the two-layer case, a look at the photographs is sufficient to 

 show that the following secondary phenomena take place at the barrier: 



1. With the flood-current salt-water passes through an increasing portion of the 

 entrance of the basin. The intermediate stratum is more and more compressed, and 

 attains its minimum sectional area at high-water at the same time as the area of the part 

 of the entrance occupied by salt-water is at its maximum; 



2. At high- water and with beginning ebb-current there is still a bottom-current of 

 salt-water running inwards down the left slope of the barrier, with a compensatorv current 

 of fresh- or mixed- water running outwards; 



3. With increasing ebb-current the upper current is accelerated and the bottom- 

 current retarded till it finally changes its direction; 



4. During the whole run of the ebb the lower boundary of the intermediate stratum is 

 falling until touching the top of the ridge, and to the right it will fall still farther, the ampli- 

 tude of this fall by far exceeding that of the upper boundary of the stratum. Thus,with f al- 

 lingtide, the sectionof the entrance occupied by mixed- water is gradually increasing. The 

 section of the intermediate stratum to the right of the ridge attains its maximum at low-water ; 



5. By the flood-current salt-water is thus introduced into the basin, and as a com- 

 pensation the ebb-current transports fresh-water and water from the intermediate stra- 

 tum outwards into the ocean. 



