428 Prof. A. M. Mayer's Researches in Acoustics. 



With a weak external battery and platinum electrodes the salt 

 was resolved into chlorine and ferrous chloride, but with a 

 strong battery into chlorine and iron — thus affording another 

 instance of the close analogy between the primary electrolysis 

 produced in the cell itself, and the secondary electrolysis that 

 may be produced by an external battery. 



L. Researches in Acoustics. 

 By Alfred M. Mayer*. — No. VII. 



[Continued from p. 365.] 



Experiments on the Reflection of Sound from Flames and Heated 



Gases. 



THE reading of the recent interesting research of Professor 

 Tyndall on " Experimental Demonstrations of the Stopp- 

 age of Sound by partial Reflections in a non-homogeneous 

 Atmosphere" (Proc. Roy. Soc. Jan. 1874; 'Nature/ Jan. 29, 

 Feb. 5), and of the subsequent paper by Mr. Cottrell " On the 

 Division of a Sound-Wave by a Layer of Flame or heated Gas 

 into a reflected and a transmitted Wave " (Proc. Roy. Soc. Feb. 

 12, 1874), caused me to turn my attention to the experimental 

 illustration of the reflection of sonorous vibrations from flames, 

 heated gases, and from sheets of cold gases and vapours. 



The following experiments are of easy execution, and show 

 in a marked manner the reflecting-powers of sheets of flame 

 and heated gas, and even 

 serve to give approximate 

 measures of these reflecting- 

 powers. 



Take two similar resona- 

 tors and place the planes of 

 their mouths at a right 

 angle; then in this angle 

 firmly fix the fork corre- 

 sponding to the resonators, 

 so that the broad face of one 

 of its prongs faces the mouth 

 of one resonator, while the 

 space between the prongs gj 

 faces the mouth of the other |j 

 resonator. (See the figure.) "1 

 By trial the two planes of 

 the fork are placed at such distances from the resonators that 



* Communicated by the Author. 



