Prof. Magnus's Hydraulic Researches. 189 



stratum is moved upwards by the vibration, or more correctlj% 

 hindered in its descent, while the strata immediately below are 

 either moved forward by the vibration or accelerated in their 

 motion. Hence the separation takes place before the separated 

 liquid has attained that great velocity, and then the ventral seg- 

 ments are formed which Savart has described. 



This mode of separation may, under proper conditions, take 

 place when the jet moves upwards as well as when it moves 

 doM^nwards, or when it moves at any angle to the horizon. 



87. When a jet of water reaches the ground a noise is produced, 

 which is sufficient, if particular precautions be not taken, to pro- 

 duce the Savart's segments in circular jets. If the jet be allowed 

 to fall into a vessel made of sheet-metal, it produces a tone which 

 still more promotes the formation of segments. If the vessel is 

 large, and the bottom only slightly, or not at all covered with 

 water, the tone is very deep and strong, and the ventral segments 

 are then more prominent*. These are particularly strong when 

 the oscillations of this vessel can be completely communicated to 

 those of the upper one, either by joining them on the stand, or 

 by connecting them by means of some substance which easily 

 transmits motion. 



88. Just as the continuity of the jet is diminished by the 

 vibration of the vessel, it is also impaired when, by removing the 

 tranquilizer, § 38, the jet assumes the spiral shape mentioned in 

 § 80. Savart's ventral segments generally make their appear- 

 ance without any tone or noise being pi-oduced in the neighbour- 

 hood, soon after the first traces of spiral motion have been per- 

 ceived at some distance from the efflux orifice. The segments 

 vanish, however, when the tranquilizer is put again in its place, 

 because then the spiral-shaped motion in the jet ceases. 



On the penetration of air-bubbles in a liquid. 



89. Jets falling into a vessel which already contains some of 

 the same liquid, cause, with but few exceptions, air to penetrate 

 into the liquid. I made experiments several years ago, in order 

 to find out under what conditions this penetration takes place. 

 These experiments were communicated to the Berlin Academy 

 of Sciences as long ago as the 8th of December, 185], but their 

 publication was deferred because they stand in intimate con- 

 nexion with these experiments on the nature of the liquid jet. 



* The changes which the tone undergoes are very surprising. The 

 strong deep tone often changes suddenly into a much higher one, and this 

 changes suddenly again. I have not further examined the reasons of these 

 changes. They probably arise from the changes in the vibration of the 

 metallic vessel when the water in it increases ; the vessel out of which the 

 water flows is set into other vibrations, and by this the form of the jet and 

 its action on the lower vessel are changed. 



