1878.] in varying the Force of an Electric Current, 363 



then filled with, well-moistened clay and water. A piece of zinc as 

 the positive element was placed upon the clay. Insulated wires were 

 attached to each plate, and three of these cells were joined in series. 

 All experiments were made on a closed circuit, the telephone being 

 used as a phonoscope to detect variations in the current and the con- 

 sequent reproduction of sound. The apparatus, or materials experi- 

 mented upon, were used in the same way as the transmitter of the 

 speaking telephone of Bell. The attached sketch will make this clear. 



B is the battery, S the source of sound or material examined, T the 

 telephone or phonoscope. 



I introduced into the circuit at S a strained conductor — a stretched 

 wire — listening attentively with the telephone to detect any change 

 that might occur when the wire was spoken to or set into trans- 

 verse vibrations by being plucked aside. Gradually, till the wire 

 broke, the strain was varied, but no effect whatever was remarked 

 except at the moment when the wire broke. The effect was but 

 momentary, but invariably at the moment of breaking* a peculiar 

 " rush " or sound was heard. I then sought to imitate the condition 

 of the wire at the moment of rupture by replacing the broken ends 

 and pressing them together with a constant and varying force by the 

 application of weights. It was found that if the broken ends rested 

 upon one another with a slight pressure of not more than one ounce 

 to the square inch on the joints, sounds were distinctly reproduced 

 although the effects were very imperfect. 



It was soon found that it was not at all necessary to join two wires 

 endwise together to reproduce sound, but that any portion of an 

 electric conductor would do so even when fastened to a board or to a 

 table, and no matter how complicated the structure upon this board, 

 or the materials used as a conductor, provided one or more portions 

 of the electrical conductor were separated and only brought into con- 

 tact by a slight but constant pressure. Thus, if the ends of the wire ter- 

 minate in two common French nails laid side by side, and are separated 



vol. xxyii. 2 B 



