On the Transmission of Vocal and other Sounds by Wires. 115 



does in all cases retard the light-wave period, or increases its 

 length. The bluing of the cobalt-glycerine solution by heat, 

 and its yellowing by cold also, are entirely in accord with the 

 before-mentioned conception. It may be noticed also that the 

 glycerine solution of a coloured salt is, as a rule, of a much 

 richer colour than the aqueous solution of the same strength, 

 by weight or volume, 



I cannot but think that these results lend considerable sup- 

 port to the idea mentioned in § 189, which idea has been so 

 far fruitful in Abney's hands that he has been enabled, by 

 associating a metallic salt with a heavy molecule, to fit the 

 vibrating period of a photographically sensitive film to the 

 light which it is desired to record. 



I have to express my indebtedness to Mr. A. K. Huntington 

 for the patience, zeal, and skill which he has shown in helping 

 me in the work of the first half of this part (No. YI.) of my 

 research. 



XV. On the Transmission of Vocal and other Sounds by 

 Wires. By W. J. Millar, C.E., Sec. Inst. Engineers and 

 Shipbuilders in Scotland*. 



1. f\BJECT of Paper. — The object of the present paper is 

 the description of a series of experiments made by the 

 author upon the transmission of vocal and other sounds by 

 wires, and the results obtained from those experiments. 



2. Transmission of Sound in general. — The transmission of 

 sound by various media is familiarly illustrated from day to 

 day ; and the readiness with which these media are affected 

 has been made the subject of many experiments. 



One familiar illustration of the transmission of sound from 

 air to solids and thence back to the air is that which occurs in 

 the vertical and horizontal partitions between rooms, such as 

 partition walls and floor and ceiling spaces — the sounds origi- 

 nating in one room being thus transmitted to the adjoining 

 room without having recourse directly to air communication. 



From a consideration of the latter, as also from other phe- 

 nomena, the author has for some time been convinced that 

 vocal sounds might be transmitted by solid bodies, such as 

 wires, and that to considerable distances. 



After several unsuccessful atttempts, the author during the 

 month of January last, having occasion to use some fine 

 copper wire, carried a portion of it out from the house to a dis- 

 tance of about 20 yards, and attached a couple of pasteboard 



* Communicated by the Physical Society. 

 12 



