230 Mr. Wheatstone on the 



If the sounds of the piano-forte are to be transmitted down- 

 wards, a brass wire, about the thickness of a goose-quill, will 

 suffice for the communication, as the weight of a reciprocating 

 instrument suspended from it below will keep it sufficiently 

 straight. To bring the conducting-wire into contact with the 

 under surface of the sounding-board of the piano- forte, an 

 aperture must be made in the bottom of the instrument imme- 

 diately below the intended point of contact ; and to ensure a 

 perfect connexion with the sounding-board, it is advisable to 

 furnish the wire with a shoulder just below its entrance into 

 the aperture, and to occasion an upward pressure on this 

 shoulder, by a piece of leather stretched on a ring (as in the 

 insulating-tube above described) and placed at the end of a 

 strong steel spring ; the other end of which is screwed firmly 

 to the bottom of the instrument. To assist in supporting the 

 wire, another shoulder may be made on it, so as to rest upon 

 the upper covering of the insulating-tube which passes through 

 the floor ; and the reciprocating instrument may be suspended 

 by inserting the end of the wire into the sounding-board, and 

 then securing it by a nut and screw on the opposite side. The 

 form of the resounding instrument is a matter of choice ; but, 

 in order to obtain the freest and loudest tones, it is requisite to 

 have the principal vibrating surface perpendicular to the con- 

 ducting-wire. It is instructive to observe the gradual changes 

 in the intensity and the quality of the transmitted sounds, 

 when the sounding-board is made to pass through the various 

 degrees of obliquity from a perpendicular direction to the con- 

 ductor, until it is in the same plane with it; or, to employ 

 Savart's language, as the communicated vibrations change 

 from normal to tangential ; in the latter case, the sounds have 

 a subdued, and what is ordinarily called a metallic quality. 

 In the first public experiments I made in 1821, the recipro- 

 cating instrument, which was the representation of an ancient 

 lyre, was so constructed as to produce tangential vibration ; the 

 tones were consequently far inferior to what I have since been 

 able to produce. The transmitted sounds are not sensibly 

 impaired when the wire is separated at several places, and the 

 disunited parts fastened together by mechanical contact ; the 

 annexed wood-cut represents the divisions of the conducting- 



