I. SOURCES. 181 



flame under a pressure just short of roaring. Such a flaine with good gas 

 can be had 2 feet high, shrinking down under the influence of a sound to less 

 ih;:n one half this height. With similar burners and pressures the quality 

 of different specimens of coal gas is accurately determined by the degree of 

 sensitiveness of the flame. See Phil. Mag., March and April 1867. 



697b. Suitable source of Sound for experiments with 

 Sensitive Flames. Prof. W. F. Barrett. 



This is simply a loud ticking watch enclosed in a padded case with a 

 movable cover, and mounted on a sliding stand. 



697c. Practical application of Sensitive Flames. 



Prof. W. F. Barrett^ 



By using a suitable burner a sensitive flame can be made to spread out 

 sideways into a fish-tail flame under the influence of sound. Under such con- 

 ditions the flame can be made to touch a compound metallic ribbon, which 

 curves by unequal expansion, closes an electric circuit, and rings an electric 

 bell. An arrangement of this kind could be adapted to detect burglars, or 

 to act as a self-recording phonoscope. First exhibited by Prof. Barrett at 

 the Koyal Dublin Society, January 1868. 



698. Set of Resonant Tubes. Prof. IV. F. Barrett. 



By suddenly and successively withdrawing the stopper, the resonance of 

 the air within the series of tubes will give the notes of the common chord. 



699. Apparatus for experiments with singing gas flames. 



Yeates $ Sons. 



The above, consisting of glass tubes of similar size, with the assistance of 

 a revolving mirror, will illustrate most of the phenomena of interference, 

 harmony, &c. 



700. Inferior Limits of Audibility. An apparatus to 

 show the lowest number of vibrations that will produce sound. 



Elliott Brothers* 



701. Sir Charles Wheatstonc's Resonating Tubs. 



W. Groves, 



By moving a piston up and down, and thus diminishing or enlarging the 

 resonator, a perfect two-octave scale of aliquot parts may be produced from a 

 spring, which would othenvise sound but one note. The scale may thus be 

 played as rapidly as by the fingers upon a pianoforte. Set the spring in 

 vibration by a twang with the forefinger of the left hand, and draw the piston 

 with the right hand. 



701 a. Sir Charles Wheatstone's original " Magic 



Lyre,'* for rendering vibrations audible at a distance through 

 wires. Robert Saline. 



704. Set of five Steel Tuning-forks on a new system. 



Dr. Stone. 



