f;r)2 'I'lii; ixvKNToivS OF TTJE 'n^rjx^ii.'APir and TJ^LEPHONE. 



for traiisinissioii, wiy liiiili speeds v.nx hv atlaiiicd by this inetlKxl of 

 record in !H' tlie sii^iuds. 



The chemical method of recordiuj; has been iiiostly used for copying- 

 or autographic telegraphs, and of these a considerable number have 

 been devised. The automatic method of transmission has been brought 

 to a higli state of i)erfection. Among others who have worked at tlie 

 subject are AVheatstone, Siemens and Halske, Gamier, Huniaston, 

 Little, Edison, Park, Thomson. 



The next important step in telegraphy was the employment of one 

 line-wire to convey moie than one message at the same time, A solu- 

 tion of tlie problem of sending two messages, one in each direction, was 

 attempted by (lintt of A'ienna, in 1853, and in the foll<»wing year by 

 Frischeu and by Siemens and Halske. These methods were not very 

 successful, but they Mere mechanically sufficient for the imrpose. 

 They however left out an important item in the account, namely, the 

 electrostatic capacity of the line. The ])roper solution of the ditticulty 

 was given by J. B. Stearns, of Boston, in 1871, who solved the problem 

 completely, so fai- at least as land lines were concerned. The same 

 principle is sufficient for all purposes, but someimportantmodifications 

 in detail are ne(;essary for submarine cables. These moditications 

 were successfully made by Muirhead, of London, and at the present 

 time duplex working is an ordinary accomplishment. The chief work- 

 ers in this field were Fris<'hen, Siemens and Halske, Stark, Edlund, 

 Gintt, Nystroin l^reece, Fur Nedden, Farmer, ]\Iaron, AVinter, Stearns, 

 and jVIuirhead. 



Next the ju-oblem of sending two messages in each direction was 

 worked out. This involves the additional problem of the simultaneous 

 sending of two messages in the same direction. The solution of this 

 problem was attempted by ])r. Wm. Gintt, of Aleuua, in 1853, and during 

 the following ten years it was worked at by Borscha, Kramer, Maron, 

 Schaak, Shreder, AVartman, and others. The first to obtain success 

 was Edison, in 1874; and his method, Avith some modificaticnis, is still 

 used. Systems of quadruplex were also invented by Gerrit Smith, in 

 1875 and 1870, of the Western Union Company, and a modification of 

 Edison's method was made by Prescott and Smith. Smith's 1876 

 method is known as the AVestern Union Company's Standard Quad- 

 ruplex. 



A system of nniltiple transmission w^as devised by M. G. Farmer, 

 of Salem, in 1852, in which, by a commutation arrangement, the line- 

 wire was ])ut snccessixely in contact with a number of local circuits. 

 A similar system was exhibited by Meyer at the A^ienna Exposition in 

 1873, and an improved form was introduced a few years ago by Delauy, 

 which is in use in several countries. These systems are of use if the 

 line-wire is capable of doing more work than any one of the stations is 

 capable of sup])lying, and may be likened to one of the main wires 

 from the central to a district telephone exchange, with this exception, 



