OP ARTS AND SCIENCES. 85 



up with an ordinary receiver, and one strike with a pencil or snap with 

 thumb and finger one of the elements, the snap will be heard at the 

 telephone. Also if a tuning-fork be held while vibrating upon one 

 of the elements, the sound will be plainly heard. I constructed a 

 single cell of copper-zinc with soldered terminals, the metals being 

 separated by a small piece of rubber tube bent so as to make a cell to 

 hold a dilute solution of sulphuric acid: the metals were about six 

 inches square. With this alone as a sender, when coupled with an ordi- 

 nary receiver, all sorts of sounds were transmitted, tuning-forks, sing- 

 ing and talking. This was then reduced in size to about that of a 

 watch ; the articulation was good, but it has never been very loud. It 

 is better when the tank is filled with water, and a battery current of 

 five or six elements inserted in the circuit. 



Second, the Reiss transmitter was modified into the form exhibited, 

 making the plate one terminal and the other a needle-point which 

 could be nicely adjusted by a screw. With this device in a circuit 

 with a battery of any sort, very strong sounds would make and break 

 the circuit, and reproduce the pitch of the sound with great loudness. 

 When the talking was gentle the articulation was very good: one 

 was able to make out every word spoken. When a drop of water 

 was placed between the plate and point, and a weak battery was used, 

 the articulation was excellent; but when a great resistance would 

 permit the use of a strong battery, so as to get a spark of considerable 

 electro-motive force, it became possible to speak and be heard at some 

 distance from the receiving telephone. During a trial of this instru- 

 ment between Boston and New York last winter, ordinary talking in 

 Boston was heard distinctly in New York, by one who was ten feet 

 distant from the receiving instrument there. 



At this time a battery of 100, 125, and 150 gravity cells were used, 

 the best results being obtained with the largest battery. The expla- 

 nation doubtless is that the air acts as the variable resistant, the vibra- 

 tions of the plate interposing a greater and less distance between it 

 and the point, the electro-motive force being sufficient at all times 

 to bridge the space. This is the more probable as I have found with 

 the same instrument, and with a greater separation of the plate from 

 the point. If a source of so-called static electricity, as with a Holtz 

 machine, be employed in place of a battery, talking is plainly heard, as 

 I have repeatedly verified over my line. 



In place of the point, surfaces of variable dimensions, of various 

 materials, and under many conditions, were tried ; surfaces of iron, lead, 

 copper, silver, carbon, in sizes varying from a point up to more than 



