372 



Mr. C. A. Bell. 



[May 13, 



brane, so arranged that the disturbances caused by impact may be 

 conducted back to the orifice, a definite musical sound is producer! . 

 The pitch of the sound, or the number of drops separated in a given 

 time, varies directly as the square root of the height of liquid in the 

 reservoir, and inversely as the diameter of the orifice. Savart further 

 showed that external vibrations impressed upon the orifice may act 

 like the impact disturbances, and cause the jet to divide into drops. 

 Impact on a stretched membrane may then cause the reproduction as 

 sound of the impressed vibrations. The tones capable of producing 

 this effect were considered to lie within the limits of an octave below 

 and a fifth above the jet normal. 



The author has found, however, that jets of every mobile liquid are 

 capable of responding to and reproducing all sounds whose pitch is 

 below that of the jet normal, as well as some above ; and that the 

 timbre or quality of the impressed vibrations is also preserved, pro- 

 vided that the jet is at such pressure as to be capable of responding 

 to all the overtones which confer this quality. Other essential con- 

 ditions for perfect reproduction are, that the receiving membrane 

 should be placed at such distance from the orifice that the jet never 

 breaks into drops above its surface ; and that it should be insulated 

 as carefully as possible from the orifice. 



In order to assist the action of aerial sound-waves on the fluid, it is 

 advisable to attach the jet-tube rigidly to a pine sound- board about 

 -fths of an inch thick. The surfaces of the board should be free, 

 otherwise it may be supported in any way. The receiving membrane 

 is formed by a piece of thin sheet rubber, tied over the end of a brass 

 tube about fths of an inch in internal diameter. A wide flexible 

 hearing tube furnished with an ear-piece is attached to the brass 

 tube. The jet-tube is connected with an elevated reservoir by an 

 india-rubber pipe. 



With an apparatus of this kind, and a tolerably wide jet-tube 

 having an orifice about 0*7 mm. in diameter, a pressure of about 

 15 decimetres of water is required to bring the jet into condition to 

 respond to all the tones and overtones of the speaking voice (except 

 hissing sounds) and those employed in music. At a somewhat higher 

 pressure it will reproduce hissing sounds. It is not easy for an un- 

 trained ear to distinguish between the disturbing sounds and their 

 reproduction by the jet, when both are within range of hearing. 

 Vibrations may however be conveyed to a jet from a distance in a 

 fairly satisfactory way, by attaching one end of a thin cord to the jet- 

 support, and the other to the centre of a parchment drum. The cord 

 being stretched, an assistant may speak, sing, or whistle, to the dis- 

 tant drum. Other devices for conveying vibrations from a distance 

 are described. 



Now when the jet is disturbed in any way, and the receiving mem- 



