THE INVENTORS OF THE TELEGRAPH AND TELEPHONE. HoS 



that all ilie corjcsixMideiicc iiocs (»ii siimiltaiu'oiisl_\ , and tlicii' need 

 be no ditticulty as to precedence. Distinctive from these is the har- 

 monic telejiiaplis of l^'Iisha Gray, Edison, and Uell. In this system, 

 whicli has been 7nost comi)letely worked out. b\' Gray, any nnmber of 

 messa<;cs may l)e sent simnltaneonsly. without reference to speed of 

 transmission. In principle, the nn^thod consists in causing- «'ach of ;i 

 number of vibrating- reeds at one end to i)ruduce pulsations of the cur- 

 I'cnt flowing' thi'ough tlie line, wliich ha^e the same ]>ei-iod as the vibra- 

 tions of the reed. A corresponding set of reeds at the receiving end of 

 the line are arrangi^d so as to b<' acted on electro- magnetically by the 

 (;urrent. Eacli of these recei>ing reeds will respond only to the i)ulsa- 

 tions of its own natural i)erit)d, an<l hence only to the vil)rations of the 

 corresponding reed at the sending end. The continuity of these vibra- 

 tions may 1k^ broken up by means of a sending key, and thus a mes- 

 sage transmitted iu the oi'dinary '']\lorse" al])habet. 



The autographic or writing telegraphic apparatus, which has been 

 developed of recent years, is of great interest, both from the fact that 

 the handwriting of the sender is reproduced in facsimile, and frctm the 

 great ingenuity of the apparatus employed. The Avritiug telegraph of 

 Cowper and the telautograph of Elisha Gray are good examples of this 

 nn)de of transmitting messages. 



In Cowper's system two rectangular components of the motion of the 

 peu are made to vary the resistaiu^e, and consequently the current, in 

 two line wires. These currents act on two electro-magnets at the re- 

 ceiving station, and the armatures of the electro-magnets are arranged 

 to produce two rectangular comp(ments of the motion of the receiving 

 pen. r>ands of paper are kept moving at approximately the same rate 

 under <'ach of these ])ens, and hence tiie chaiacters traced by the nu)tions 

 of the transmitting pen are reproduced with considerable accuracy by 

 the recei\ing ])en in consciiuence of the varying positions of the arma- 

 tures of the reccixing magnets, caused by the variations of tlie current. 

 In Gray's apparatus t\\<> lectangular components of the motion of the 

 transmitting pen s<'nd ])ulsatory currents into tlie line wire. These 

 ])ulsatory currents cause coircs])onding movements of the armatiir(\s 

 of two receiving magnets, which are made to move the receiving ])en in 

 corresponding directions, and through ])i<)poitionate distances. Sepa- 

 rate electro-inagnetic arrangements lift tlie pen off the ]>ai)ei- l>etween 

 the words and at the eml of tlie lines, and allow the icceiving jx'n to be 

 moved backwards or foiwards withont marking the pajx'r. Still 

 another electro-nnignetic arrangement is used to iiio\e the ])aper for- 

 ward between the lines. The whole ap))aratus is exceedingly ing<'nious, 

 l>ut iiiiich too exteiisixc iind coni|>li(at('d to admit of clear description 

 here. 



Although ihe mere extension of tclegi'aplis t'rdiii land to submarine 

 lines can hardly be called an iii\"eiit ion. yet very m. my new problems 

 presented thenisehes for solution in this extension. Many of these 



