388 



Prof. Tyndall on the Action of Sonorous 



Fig. 18. 



Fig. 19. 



exhibits. The drops, as they Fig. 17. 

 descend, are continually chan- a 



ging their forms. When first 

 detached from the end of the 

 limpid portion of the vein the 

 drop is a prolate spheroid, with 

 its longest axis vertical. But a 

 liquid cannot retain this shape 

 if abandoned to the forces of its 

 own molecules. The spheroid 

 seeks to become a sphere. The 

 longer diameter therefore short- 

 ens; but, like a pendulum, which 

 seeks to return to its position of 

 rest, the contraction of the verti- 

 cal diameter goes too far, and the 

 drop becomes a transversely ob- 

 late spheroid. Now the con- 

 tractions of the jet are formed 

 at those places where the long- 

 est axis of the drop is vertical, 

 while the swellings appear where 

 the longest axis is horizontal. 

 It will be noticed that between 

 every two of the larger drops is 

 a third of much smaller dimen- 

 sions. Whenever a large drop is 

 detached, by a kind of kick on 

 the part of the retreating vein, J|] 

 a little satellite is shaken after 

 it. According to Savart, their 

 appearance is invariable. 



This breaking up of a liquid 

 vein into drops has been a sub- 

 ject of much discussion. I hold 

 it to be due to the tremors im- 

 parted to the water by its friction 

 against the boundaries of its ori- 

 fice. To this point Savart traced 

 its pulsations, though he did 

 not think that friction was their 

 cause. Whatever their cause 

 may be, the pulsations exist, and 

 they are powerfully influenced 

 by sonorous vibrations, which render the limpid portion of the 

 vein shorter than it would otherwise be. In the midst of a large 

 city it is hardly possible to obtain the requisite aerial tranquillity 



