494 NEGRETTI AND ZAMBRA, HQLBOEN VIADUCT, B.C , 



EXPERIMENTS TO ILLUSTRATE ACOUSTICS. 



Each. Each. 



s. d. s. d. 



3056 Apparatus for producing Musical Sounds with a jet of 



Hydrogen Gas burning in a glass tube, Musical Flames 1 10 



3057 Apparatus for exhibiting a Rotating Singing Flame from 4 16 6 



3058 Trevyllian's Experiment, or Rocking Bar, for producing 



sound by the vibrations of a Heated Copper Bar upon 



a Cold Block of Lead ... ... 18 



3059 Bell Experiment, for proving sound depends upon the 



presence of Air (see also page 473) . . . . 15 1 10 



3060 Improved Arrangement of the Experiment, with 



Electro Magnetic Apparatus for setting the Bell 

 in motion, having a glass receiver, fitted with two 

 stopcocks, for experimenting upon the different gases 4 10 



3061 Polarization of Sound, Apparatus for demonstrating, 



consisting of a Tuning Fork and Glass Flask . 10 6 



3062 Monochord, of simple construction, with adjusting 



weights, for altering the tension of the vibrating 

 string, for showing the relation and sub-division of 

 musical sounds 6 10 



3063 Brook's Apparatus, to show the relation between the 



tension of a chord and the time of vibration . . 2 10 



3064 Apparatus for exhibiting the vibration of elastic mem- 



branes by sand upon their surfaces (or Chladni's 



Acoustic Figures) ....... 1 12 



3065 Steel Spirals, for producing various musical sounds, 



mounted on a sounding board, with a hammer . 300 



3066 Syrene, for ascertaining the number of impulses, in a 



given time, required to produce any particular note. 

 This is done by a clockwork movement, arranged to 

 record the movement of a disc of metal, perforated 

 with a series of holes, through which a current of air 

 is forced . 550 



3067 Wheatstone's Kaleidophone, to exhibit the principle of 



the superposition of small vibrations .... 1 10 



3068 Organ Bellows, with double riser, wind chest, and sound 



board, with a set of wood and metal tongued pipes, 



for producing musical sounds 10 10 



3069 Vibration Telephone. Not Electrical. Speaks Loudly and Clearly. Simple 

 ahd cheap. In this apparatus a well-known principle of acoustics is practically 

 applied. It consists of a Sound Box at each end, fitted with a properly insulated 

 and stretched Wire between them. For distances of 30 to 1000 feet it will act well. 



Vibration Telephone, with Electric Call arrangement. 2 Telephones, 

 6 Insulators, 200 feet of suitable Wire, 2 Bells, 2 Keys and 2 Batteries 

 complete, with instructions for fixing up and use . . . 5 12 6 

 Telephones and Transmitters (except for Export} cannot be supplied. 



The various Acoustic instruments, &c., invented and used by Messrs. Savart, 

 Wheatstone, Biot, Tyndall, Konig, Helmholtz, Lissajous, Leon, Scott, and others, 

 in their researches connected with Sound, described in Ganot's Physics, 

 constructed and supplied to order, by Negretti and Zambra. 



