PHYSICS. 447 



smooth tubes the diminution of velocity is proportional to r-^ and to 

 n-^, as determined by Helmholtz; (5) that the velocity in free air for 

 sound waves of low intensity, or just audible, is 331. G7G meters at O^C; 

 and (6) that the ratio between the two specific heats of air, as deduced 

 from the Newtonian velocity, 279.955 meters, and the above value, 331.076 

 meters, is 1.4030. {Phil. Mag., October, 1884, V, xviii, 328.) 



Eayleigh has examined the conditions of sensitiveness of smoke-jets 

 and jets of colored liquid, paying especial attention in the former to 

 the illumination, and exalting the effect by means of resonators. The 

 maximum sensitiveness was reached at 250 vibrations. By using the 

 stroboscopic method, the serpentine motion of the jet previous to rupture 

 was clearly seen. For liquid jets, water colored with permanganate was 

 used in water containing ferrous sulphate. The notes ibr maximum 

 sensitiveness were far lower than for smoke jets, forks vibrating from 

 20 to 50 times a second producing the maximum efiect. This is due, 

 not to the difference of density, but to a difference of viscosity. (Phil. 

 Mag., March, 1884, V, xvii, 188.) 



Fuchs has suggested a simple method of analyzing the vowel sounds, 

 which is easy to put in practice. One of the ears is closed with a piece 

 of wet tissue paper, and to the other is api^lied one end of a rubber 

 tube tipped with horn, the other end being placed iu the mouth. The 

 mouth is then given the configuration corresponding to the vowel A, 

 for example, and the various keys of a piano in good tune are struck, 

 beginning with the highest notes of the scale. The mouth cavity acts 

 like a resonator, so that when a note is struck which accords with it 

 this note is re-enforced by resonance and appears stronger than the others. 

 In this way the harmonics which are characteristic of the vowel for 

 which the mouth is set may be easily determined. The sonometer may 

 be used in this experiment in place of the piano. ( Wied. Ann., xxi, 

 513; J. Phys. II, iii, 548; Phil. Mag., May, 1884, V, XVii, 410.) 



Melde has investigated the effect of placing the vibrating fork at a 

 position on a string other than its extremity. If it is at the middle 

 point, the vibrations are symmetrical and the two halves take identical 

 forms. Since the point of attachment cannot be a node, the cord does 

 not vibrate if the sound of the fork is that of an even harmonic of the 

 cord. In short, each half vibrates as if it was an entirely distinct string, 

 vibrated at their common extremity. If the fork is not at the middle 

 point, the form of the string during the vibration is dissymmetrical witli 

 relation to the middle. The forks were vibrated electrically. ( Wterf. 

 Ann., XXI, 452; J. Phys., December, 1884, II, iii, 547.) 



Thompson has given an illustrated description of the sound-mills con- 

 structed by Dvorak. Two of these act by the repulsion of resonant- 

 boxes. In the first four, resonators are mounted so as to revolve horizon- 

 tally ; in the second the resonator is a cylindrical box, which revolves 

 on its axis. The third is called a "sound radiometer" and the fourth 



