46 ZEILOX, ON TI DAL BOUNDARV-WAVES. 



Explanation of the Plates. 



Pl. I. Series of 6 photographs taken at intervals of about half a second, sliowing the generation of waves 

 in the boundary above the ridge and their propagation on both sides of it (p. 36). To the left of the ridge is visible 

 a small pendulum indicator, moving with the water, and showing the direction and intensity of the current. (For 

 instance the current is running leftwards with its maximum velocity in fig. 2, and has changed its direction be- 

 tween figs. 3 and 4. ) 



Pl. II. Series of photographs, illustrative of the two-layer case of the »second experiment » (p. 37 ), and covering 

 about a period of the motion of the wave-generating pendulum. 



Pl. III. Figs. 1—2. Two-layer case of the same experiment, with intensely-working pendulum, showing 

 a »cascade » of saltwater across the barrier. 



Figs. 3 — 6. Series of 4 photographs of the three-layer case. At the left end the lower weight of the pendulum 

 and (dimly) the moving brass lamel inside the tank are visible. 



Tryckt den 24 januari 1912. 



Uppsala 1912. Almqvist & Wiksells Boktryckeri-A. -B. 



