134 



Lord Kayleigh. 



[June ]5, 



Although, the multiple streams are better separated when the jet is 

 originally directed upwards at an angle of about 45°, I preferred to 

 use a horizontal direction as giving simpler conditions. The velocity 

 and diameter are then practically constant throughout the transfor- 

 mation, and may be readily calculated from observations of the head 

 and of the total quantity of fluid discharged in a given time. The 

 reservoir consisted of a large glass bottle, provided with a tubulure 

 near the bottom. Into this was fitted a 1-inch brass tube, closed at 

 the end by a flat plate, in which a circular aperture was pierced of 

 about ^ of an inch in diameter. 

 If h = head, 



d— diameter of jet, 

 v= velocity of issue, 

 V= volume discharged in unit time, 



then i 7r drv=Y, v=S(2gh). 



Again, if N 7 be the frequency of the most rapid vibration which 

 can influence the jet, we have by Plateau's theory — 



N'=— = vl — ( 2 ff 7l ) f 



If N" be the frequency of the principal note of the jet, then, as 

 explained in my former paper, 



-^_3\L42 jj., 

 4-508 



In the present experiment it was found that 1050 cub. centims. 

 were discharged in four minutes, and the head was 7f inches, so that 

 in C.G.S. measure — 



7*=7fx2-54; 0=981; 



240 



whence N'=372, N=259. 



As sources of sound tuning-forks, provided with adjustible sliding 

 pieces, were empLoyed, except when it was important to eliminate the 

 octave as far as possible"; the vibration was communicated to the 

 reservoir through the table on which it stood. The forks were 

 either screwed to the table and vibrated with a bow, or mounted on 

 stands (resting on the table) and maintained electrically. The 

 former method was quite adequate when only one fork was wanted at 

 a time. 



With pitches ranging from 370 to about 180, the observed phenomena 

 agreed perfectly with the unambiguous predictions of theory. From 

 the point — decidedly below 370 — at which a regular effect was first 



