550 THE POPULAR SCIENCE MONTHLY. 



rent-regulator, identical with the combination used by Reis. Too 

 loud shouting in either the Reis or Blake transmitters spoils the ar- 

 ticulation by breaking the circuit. 



Reis's transmitters have been called make- and break-circuit instru- 

 ments. If so, the Berliner and Blake transmitters, operating on the 

 same princijile, are also make- and break-circuit instruments. If, on 

 the other hand, the Berliner and Blake transmitters, by their current- 

 regulators, determine undulatory electric currents, in correspondence 

 with the sound-waves, the Reis transmitters, by the same mechanism, 

 necessarily do the same. 



The identity of the mechanism of the current-regulators in four of 

 Reis's transmitters with the mechanism in six modern forms of trans- 

 mitter is strikingly exhibited by Professor Thompson in a compara- 

 tive plate. 



In connection with the Reis current-regulator, now in almost uni- 

 versal use, it has been in later times found generally advisable to use 

 an induction-coil. It is an interesting fact in the evolution of the 

 telephone, though it may not be stated in the book before us, that 

 Ferguson's chemistry, published in 1868, states that Dr. Wright in 

 England used a Reis transmitter in the primary circuit of an induc- 

 tion-coil. The combination of current-regulator and induction-coil in 

 the modern transmitters is therefore old. 



In the third section of the appendix, Reis's receivers are comjjared 

 with recent instruments. The examination in this case, also, is much 

 aided by a comparative plate. Reis's electro-magnetic receiver is 

 shown to combine the three following essential elements, which enter 

 into the Yeates, Gray, Bell, Edison, and other receivers : 1. An arma- 

 ture acted on by an electro-magnet ; 2. An armature elastically mount- 

 ed ; 3. An armature of sufficiently extended surface to set in motion 

 aerial sound-waves. This discussion has been anticipated in previous 

 pages. Professor Thompson, in summing up his close analysis, points 

 to Reis as the genius by whom the essential principles of all the elec- 

 tro-magnetic receivers now in use were discovered and combined so 

 as to reproduce articulate speech. 



A section in the appendix is devoted to the "undulatory" cur- 

 rent in Reis's telephone. We have already seen that the function of 

 the Reis transmitter was to vary the strength of the electric current, 

 and not to break it. Reis was accustomed to speak of opening and 

 closing the circuit in describing these instruments, not in the techni- 

 cal sense of modern telegraphy, nor with the idea of sending inter- 

 mittent signals, but in the sense of increasing or diminishing the 

 current, without going so far as absolutely to break it. This is abun- 

 dantly proved by the context in his descriptions, and by the operation 

 of his instruments. He states, in his first memoir, that, to reproduce 

 any sound, or combination of sounds, all that is necessary is to set up 

 in the receiver vibrations whose curves are identical with those of the 



