294 PLEASANT WAYS IN SCIENCE. 



were produced by the point of the receiving apparatus. The 

 paper diaphragm being thus set into vibrations of the re- 

 quisite kind in number, depth, and side-range, there are pro- 

 duced precisely the same sounds that set the diaphragm of 

 the receiver into vibration originally. Thus the words of 

 the speaker are heard issuing from the conical drum in his 

 own voice, tinged with a slightly metallic or mechanical tone. 

 If the cylinder be more slowly turned when transmitting than 

 it had been when receiving the message, the voice assumes 

 a base tone ; if more quickly, the message is given with a 

 more treble voice. " In the present machine," says the 

 account, " when a long message is to be recorded, so soon 

 as one strip of tinfoil is filled, it is removed and replaced by 

 others, until the communication has been completed. In 

 using the machine for the purpose of correspondence, the 

 metal strips are removed from the cylinder and sent to the 

 person with whom the speaker desires to correspond, who 

 must possess a machine similar to that used by the sender. 

 The person receiving the strips places them in turn on the 

 cylinder of his apparatus, applies the transmitter, and puts 

 the cylinder in motion, when he hears his friend's voice 

 speaking to him from the indented metal. And he can re- 

 peat the contents of the missive as often as he pleases, until 

 he has worn the metal through. The sender can make an 

 infinite number of copies of his communication by taking a 

 plaster-of-Paris cast of the original, and rubbing off impres- 

 sions from it on a clean sheet of foil." 



I forbear from dwelling further on the interest and value 

 of this noble invention, or of considering some of the 

 developments which it will probably receive before long, 

 for already I have occupied more space than I had intended. 

 I have no doubt that in these days it will bring its inventor 

 less credit, and far less material gain, than would be acquired 

 from the invention of some ingenious contrivance for destroy- 

 ing many lives at a blow, bursting a hole as large as a church 

 door in the bottom of an ironclad, or in some other way 

 helping men to carry out those destructive instincts which 



