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



as to rest partly on grass, and fastened up at the ends to pins ; 

 attachments wore made, and vocal sounds transmitted: whis- 



tling and the tuning-fork sounds very clearly heard, although 

 a high wind was blowing at the time. 



4. The Mouth- and Ear-pieces. — The mouth- and ear-pieces 

 used in these experiments have been of various materials and 

 forms. The materials tried have been pasteboard, wood, gutta- 

 percha, india-rubber, parchment, iron, tin, and zinc. These 

 have generally been arranged as disks or drums, having a 

 more or less extended rim around them to confine the 

 sounds. This rim has been of cylindrical, conical, and other 

 forms. 



In general, greater volume of sound accompanied increased 

 depth of rim ; but the sounds were hardly so distinct as when 

 the rim was kept shallower. 



The wire was usually attached to centre of disk ; but in 

 some cases good results were got where the wire was led 

 through a cylindrical hollow piece of wood and terminated 

 close to the disk ; indeed a hollow piece of wood without a 

 disk did very well. 



As a rule, the effects seemed better when the wire was led 

 outside of the house. 



High-pitched voices are more easily heard than deep strong 

 roices. 



In the experiments with the telegraph-wire one of the disks 

 used was of thin sheet-iron 3| inches in diameter. Set in a 

 wooden rim about -J inch deep, the wire was fastened into a 

 small piece of wood, which in turn was cemented dow r n to 

 centre of disk. The tuning-fork sounds were very w T ell heard 

 with this arrangement ; and one peculiarity was that, on the 

 wooden fastening accidentally breaking away from the iron, 

 the sounds could again be heard by holding the disk in one 

 hand and pressing the wooden termination of the wire upon 

 the disk with the other. 



5. Wires. — The wires, as a rule, require to be more or less 

 tightened up ; but this varies with the heaviness of the wire. 



The sound is increased with a tight wire. 



The volume of sound appears to be increased with a heavy 

 wire. Thus in the telegraph-wire about \ inch thick, pro- 

 bably No. 8, the sounds were stronger and fuller than in the 



