238 Mr. Wheatstone on the Transmission, fyc. 



glass, cane, or deal-wood rods, with the velocity of about 

 18,000 feet per second, so that it would travel the distance of 

 200 miles in less than a minute. 



When sound is allowed to diffuse itself in all directions as 

 from a centre, its intensity, according to theory, decreases as 

 the square of the distance increases ; but if it be confined to 

 one rectilinear direction, no diminution of intensity ought to 

 take place. But this is on the supposition that the conduct- 

 ing body possesses perfect homogeneity, and is uniform in its 

 structure, conditions which never obtain in our actual experi- 

 ments. Could any conducting substance be rendered perfectly 

 equal in density and elasticity, so as to allow the undulations 

 to proceed with a uniform velocity without any reflections or 

 interferences, it would be as easy to transmit sounds through 

 such conductors from Aberdeen to London, as it is now to 

 establish a communication from one chamber to another. 

 Whether any substance can be rendered thus homogeneous and 

 uniform remains for future philosophers to determine. 



The transmission to distant places, and the multiplication 

 of musical performances, are objects of far less importance 

 than the conveyance of the articulations of speech. I have 

 found by experiment that all these articulations, as well as the 

 musical inflexions of the voice, may be perfectly, though feebly, 

 transmitted to any of the previously described reciprocating 

 instruments by connecting the conductor, either immediately 

 with some part of the neck or head contiguous to the larynx, 

 or with a sounding-board, to which the mouth of the speaker 

 or singer is closely applied. The almost hopeless difficulty of 

 communicating sounds produced in air with sufficient intensity 

 to solid bodies, might induce us to despair of further success ; 

 but could articulations similar to those enounced by the human 

 organs of speech be produced immediately in solid bodies, their 

 transmission might be effected with any required degree of 

 intensity. Some recent investigations lead us to hope that we 

 are not far from effecting these desiderata; and if all the 

 articulations were once thus obtained, the construction of a 

 machine for the arrangement of them into syllables, words, 

 and sentences, would demand no knowledge beyond that we 

 already possess. 



