320 HENRY AND THE TELEGRAPH. 



^'- Relay'''' and " I'ccciving^^ circuits. — The somewhat controverted ques- 

 tion as to the true origin of the rehiy system of electrical communica- 

 tion has been purposely reserved for a concluding discussion. Though 

 unquestionably a valuable adjunct in distant intercourse, the " relay " 

 is not here treated as an essential feature of the electric telegraph, since 

 land-lines of GOO miles, and by the ocean system cables of 2,000 miles, 

 are easily made operative in a single stretch or circuit. 



Henry's original contrivance of a special compound circuit in 1835, 

 (already noticed,) by no means precluded an equally original invention 

 by Professor Morse some years later of a different arrangement of con- 

 ioined circuits. Nor is it at all surprising that a combination (in itself 

 sufficiently obvious) should spontaneously occur to several minds if so 

 circumstanced as to feel a need for it. There is reason to believe that 

 Morse, like Wheatstone, independently invented his application of the 

 general idea, and probably about the same time, in the spring of 1837.* 



To do justice however to each party, it is all-important to discrimi- 

 nate carefully between the actual results attained by each. Henry had 

 simply the ])hilosopliic plan of employing a weak magnetic power to act 

 as a distant trigger for a great magnetic power, (one therefore of short 

 circuit,) — and there stop.t Wheatstone, employing a delicate arrange- 

 ment of silent galvanometer needle at the distant station, felt the neces- 

 sity of i)romi)tly calling attention to the visual signal by an audible 

 alarm; hence this feeble i)Ower was used also as the trigger to bring 

 into action a much shorter and more powerful electro-magnetic circuit, 

 — but merely as a call, and there stop. Morse, requiring a stronger sig- 

 naling duty (in the use of a recording lever) than the length of the 

 circuit would probably permit, conceived the idea of a division of the 

 circuit into several shorter ones; each successive circuit to be of the same 

 Mnd as the j)recediug. He thus first produced a true "relay," and this 

 too without a knowledge of anything similar haviug been previously 

 exhibited by Professor Henry as a lecture-room experiment before his 

 college classes. It may therefore be affirmed that Henry, feeling no 

 occasion for extending a telegraphic line, had probably no idea of a 

 "relay," proi)erly so called, when he first devised his combination of an 

 "intensity" circuit with a "quantity" circuit; that Professor Morse, by 

 Ms own declaration, had certainly no conception of a local receiving 

 "quantity" magnet when subsequently he first devised his combination 

 of a series of equal "intensity" circuits; and that Wheatstone had as 

 little idea of either a "receiving" or a "relay" magnet when (in con- 



* It even appears (from the uufortnuate controversy between Messrs. Cooke and 

 Wlieatstone as to the priority and vahie of their respective contributions) that the two 

 English copartners cacli independently invented the "relay" alarum. {Profcsaor 

 W heatstone' s Annwer to Mr. Cooke's pamphlet. Rexjublished in Cooke's '^Electric Tiie- 

 grapli" etc. part i, p. 55, foot-note.) 



t "My object in the process described by me was to bring into operation a Large 

 'quantity' magnet connected witli a 'quautitj'^' battery in a local circuit, by means of 

 a small 'intensity' magnet, and an 'intensity' battery at a distance." {iSmiihsouian 

 lieport for 1857, p. 112.) 



