180 SEC. 6. SOUND. 



Thu profit pyrophone, which this model represents, has three octaves like 

 those of a piano, and is composed of a series of glass tubes, similar to organ 

 pipes, of different lengths and dimensions, in which gas jets burn. A very 

 simple mechanism causes each key to communicate with the corresponding 

 supply pipe of the flames in the glass tubes. On pressing the keys, the 

 flames separate and the sound is produced as soon as the little jets in each 

 tube are separated from each other ; when re-united and becoming one flame, 

 the sound immediately ceases. 



In this instrument it is shown that when two or more flames are introduced 

 in a tube they vibrate in unison, and produce a musical sound when they are 

 placed one-third the length of the tube, and a new law has been demon- 

 strated, as an application of which an instrument which approaches the human 

 voice more nearly than any yet made has been constructed. 



A contrivance opens and shuts like the fingers of a hand, at the extremities 

 of each of which a small jet of gas is lighted. When the fingers are separated, 

 the sound is produced ; when they are closed or approach each other, the 

 sound ceases, and the numerous jets become one silent flame. 



The new principle is as follows : "If two or more flames of a certain size 

 " be introduced into a tube made of glass or other material, and if they be 

 M so placed that they reach to the third part of the tube's height (measured 

 " from the base), the flames \vill vibrate in unison. This phenomenon con- 

 " tinues as long as the flames remain apart, but as soon as they are united the 

 a sound ceases." 



The pyrophone gives sonorous and penetrating tones, and may be con- 

 structed from one octave to a most extended compass, and for the cabinets 

 de physique, with one, two, three, or more notes to show the principle of the 

 " interference " of singing flames. The exhibitor has also invented a gaselier 

 (lustre chantanC), lighted by electricity, which can be placed in the centre of 

 a room, and by unseen electric wires be made to produce powerful and 

 melodious sounds, and on which any kind of music can be performed. 



696. Tube for Singing Flames, according to Schaff- 



gotsch's system. Albrecht, Tubingen. 



697. Set of Glass Tubes for illustrating singing flames, 

 with paper sliders for adjusting the pitch of any tube. 



Prof. W. F. Barrett. 



The only novelty here is the paper sliders, which enable the pitch of the 

 note to be readily adjusted, and were originally suggested by the exhibitor. 



697a. Stand and Burner for Sensitive Flames. 



Prof. W. F. Barrett. 



The sensitive flame is an illustration of resonance. The vibrations accepted 

 by the flame are those which the flame itself would emit when roaring. A 

 flame to be sensitive must be brought to the verge of roaring by a proper 

 adjustment of pressure on the gas supply. The flame is then in unstable 

 equilibrium, and a feeble sympathetic vibration will then produce the same 

 effect on the flame as a slight increase in the gas pressure. 



The flame to be extremely sensitive must be fed with gas which flows 

 smoothly and freely to the orifice. A bell gas holder is far better than a gas 

 bag for obtaining the necessary pressure. The gas cocks must be fully open 

 and the pressure adjusted by altering the weights on the gasholder' The 

 stand shown allows the gas to flow smoothly, and the best burner is a steatite 

 " jet photometer " burner carefully enlarged till it gives the tallest possible 



