138 



Lord Rayleigk. 



[June 15, 



and its diameter diminishes, so that the degree of instability soon 

 becomes small. On the other hand, the kind of disturbance which 

 will be effective in a later stage is altogether ineffective in the earlier 

 stages. The change of conditions during fall has thus a protective 

 influence, and the continuous part tends to become longer than 

 would be the case were the velocity constant, the initial disturbances 

 being unaltered. 



I have made many attempts to determine the origin of the dis- 

 turbances which remain in operation when the jet is protected from 

 ordinary tremors, but with little result. By suspending the reservoir 

 with india-rubber straps, &c, from the top of a wooden tripod, itself 

 resting upon the stone floor of one of the lower rooms of the Cavendish 

 Laboratory, a considerable degree of isolation was attained. A stamp 

 of the foot upon the floor, or the sounding of a note of suitable pitch 

 of moderate intensity in the air, had no great effect. Without feeling 

 much confidence I rather incline to the opinion that the residual 

 disturbances are of internal origin. As the fluid flows up to the 

 aperture along the inner surface of the plate which forms the bottom 

 of the reservoir, eddying motions are almost certainly impressed upon 

 it, and these may very possibly be the origin of the ultimate disin- 

 tegration. With the view of testing this point, I arranged an 

 experiment in which the velocity of the fluid over the solid walls 

 should be as small as possible. 



AB (fig. 1) represents a large brass tube, to which a smaller one 

 is soldered at B, suitable for india-rubber connexion. The bottom of 



