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THE POPULAR SCIENCE MONTHLY. 



of the vertical vibrations, of which the bottom of the vessel be- 

 comes the seat, and which it communicates to the whole jet. 



The tongue-shaped sheet is bordered on its outer edge, as we 

 have already shown, by swellings or cords, when everything is 

 rigorously symmetrical ; these two cords, meeting at the base of 



Fig. 18. Instantaneous Photograph showing the Cords formed on the Edges of 

 Liquid Tongues, as is seen in Fig. 14. 



the tongue and flattening against one another, form a second sheet 

 in a plane perpendicular to the former one and so on. But when, 

 for any reason, on account of the slight inclination of the canal, 

 for example, it happens that the two cords do not exactly meet, 

 one passes before the other, and one of two things may result. 

 They will either roll up upon one another like a corkscrew and 



Fig. 19. Photograph showing the Tremulousness peculiar to Cascades with Broad 



Sheets. 



follow a helicoidal course (Fig. 12, xxii, and 13), or else, by some 

 trifling cause they will miss, and, lanced in opposite directions, 

 without regarding the thin median sheet that connects them, they 

 will go each to its own side, never to find one another. The pri- 



