Notices respecting JVew Books. 141 



and causing corresponding variations in the intensity of an electro- 

 magnet placed at another point of the circuit, where these varia- 

 tions produce vibrations precisely resembling the original vibrations. 

 In Dolbear's telephone the electromagnets are replaced by perma- 

 nent magnets surrounded by helices : the receiving and transmitting 

 diaphragms are precisely alike, and, in place of a membrane, consist 

 of small disks of thin iron plate. The vibrations of the one plate 

 induce magneto-electric currents, which vary the force of the mag- 

 net at the other end of the circuit and thereby produce correspond- 

 ing vibrations in the other plate. The peculiarity of this form of 

 the instrument is that its action is reciprocal ; either end may be 

 the receiver, and the other the transmitter. The chapter also con- 

 tains an account of several of the improved forms of the Telephone ; 

 but with these we are not concerned. The main point consists in 

 the dates assigned to these three inventions ; and these dates, we 

 may observe, are by no means stated with due distinctness. Our 

 author tells us that Mr. Elisha Gray, of Chicago, invented his me- 

 thod subsequently to the spring of 1874 (pp. 14, 15); that Pro- 

 fessor A. G. Bell, of the Boston University, exhibited his instru- 

 ment, in the summer of 1876, at the Centennial Exhibition in 

 Philadelphia (p. 16) ; and that Professor A. E. Dolbear, of Tufts 

 College, made his improvements in the ensuing autumn (p. 19). 

 This is, perhaps, a sufficient statement of Mr. Prescott's case. In 

 the following chapters he allows the several claimants to speak for 

 themselves : — Chapter iL contains Professor Bell's account of his 

 researches, in a lecture delivered to the Society of Telegraphic 

 Engineers ; chapter v. Mr. Gray's account of his experimental 

 researches ; and chapter viii. an abstract of " Researches in Tele- 

 phony," by Professor A. E. Dolbear. 



The above statement suggests one or two remarks : — First. It 

 does not seem clear from chapter viii. that Mr. Dolbear claims 

 priority of invention ; but if he does, the claim does not appear to rest 

 on documentary evidence. Secondly. In chapter v. we fail to find 

 any confirmation of the date apparently given on page 14 for Mr, 

 Gray's invention, which we have very briefly described above, viz. 

 the spring of 1874*. We do, indeed, find a very surprising coinci- 

 dence, viz. " a verbatim copy " of Gray's specification and of Bell's 

 specification, both filed in the United-States Patent Office on the 

 same day, viz. Eeb. 14, 1876. In the former of these documents 

 Mr. Gray says, " I claim as my invention the art of transmitting 

 vocal sounds or conversations telegraphically through an electric 

 circuit " (p. 205) ; while in the latter Mr. Bell claims, inter alia, 

 " the method of, and apparatus for, transmitting vocal or other 



* Strictly speaking, Mr. Prescott says that in the spring of 1874 Mr. 

 Gray " invented a method of electrical transmission by means of which 

 the intensity of tones, as well as their pitch, was properly reproduced at 

 the receiving station" (p. 14), and that subsequently he invented the Te- 

 lephone above described. (t Subsequently 1 ' may, of course, mean any 

 thing. We think, however, that the suggestion of the passage (pp. 14, 15) 

 is as above stated. In chap. v. there is no trace of the Telephone until a 

 few weeks before the date of the specification, viz. Feb. 14, 1876. 



Phil Mag. S, 5, Vol. 7. No. 41. Feb. 1879. M 



