THE TELEPHONE. 



possible a more splendid array of flowers, and a busier crowd of bees, in the 

 years to come. We cannot, therefore, do better than improve the shining hour 

 Helping forward the cross-fertilization of the sciences. 



pofmD ^ -o further, I wish to express my obligation to Mr Garnett for 

 the able sssistsntr he has given me. He has not only collected the apparatus 

 before you, but constructed some of it himself. But for him, I might have 

 given you some second-hand information about telephones. He has made it 

 ptmiMft ^ you to hear something yourselves. I have also to thank Mr Gower, 

 who has brought his telephone harp, and Mr Middleton, who has contributed 

 several instruments of his own invention. 



We shall begin with the telephone in its most obvious aspect, as an 

 instrument depending on certain physical principles. 



The apparatus consists of two instruments, the transmitter and the receiver, 

 doubly connected by a circuit capable of conducting electricity. The speaker 

 lfc to the transmitter at one end of the line, and at the other end of the 

 line the listener puts his ear to the receiver, and hears what the speaker says. 



The process in its two extreme stages is so exactly similar to the old- 

 fashioned method of speaking and hearing that no preparatory practice is 

 required on the part of either operator. 



We must not, however, fell into the error of confounding the principle of 

 the electric telephone with that of other contrivances for increasing the distance 

 at which a conversation may be carried on. In all these the principle is the 

 same as in the ordinary transmission of sound through the air. The different 

 |H>rtions. of matter which intervene between the speaker and the hearer take 

 part, in succession, in a certain mechanical process. Each receives a certain 

 motion from the portion behind it and communicates a precisely similar motion 

 to the portion in front of it, in doing which it gives out all the energy it 

 received, and is again reduced to rest. 



The medium which takes part in this process may be the open air, or air 

 confined in a long tube, or some other medium such as a brick wall, as when 

 we hear what goes on in the next house, or a long wooden rod, or a metal 

 wire, or even a stretched string. In all these it is by the actual motion of 

 the successive portions of the medium that the message is transmitted. 



In the electric telephone there is also a medium extending from the one 

 instrument to the other. It is a copper wire, or rather two wires forming a 

 dosed circuit. But it is not by any motion of the copper that the message 



