290 HENRY AND THE TELEGRAPH. 



pable of beinsc excited at very great clistauces from a suitable " intensity" 

 battery. And there can be no doubt that a simihir combination of " in- 

 tensity" batter}^, with a very long coil galvanometer (such as had pre- 

 viously been found inoperative), was alone wanting to have rendered the 

 early telegraph of Schilliug a popular and commercial success. 



In the second place, this experimental arrangement of Henry was the 

 first electro-magnetic telegraph employing the armature as the signaling 

 device; or employing the attractive ])0\\Gr of the intermittent magnet, as 

 distinguished from the directive action of the galvanic circuit. That is 

 to say, it was strictly speaking the first " magnetic telegraph." 



In the third place, it was the first acoustic electro-magnetic telegraph. 

 One practical inconvenience of the "needle" system has been found to 

 ibe the perfect silence of its indications ; and hence in almost every case 

 Sk call-alarm has been required to insure attention to its messages. In 

 this respect the intermittent magnet presents the advantage, not merely 

 of a greater mechanical power from the same galvanic current, and thus 

 of a better adaptation for striking a bell at a distance, but of being in 

 itself an audible sounder by the mere impacts of its armature.* 



It is suggestive to consider for a moment how different would have 

 been the popular estimate of Henry's labors, (and especially the practi- 

 eal estimation of subsequent patentees), if the modest discoverer and in- 

 ventor had been " worldly-wise " enough to secure an early patent on 

 these three indisputably original and most pregnant features of teleg- 

 raphy : — to contest which no rival has ever appeared.! 



In 1832, Henry was elected to the chair of natural philosophy in the 

 college of New Jersey, at Princeton. In 1834, he constructed for the 

 laboratory of this college an original and ingenious form of galvanic bat- 

 tery, comprising eighty-eight elements, (each having an active zinc sur- 

 face of one and a half square feet,) of which anj* number, from a single 

 pair upward, could be brought into action ; while by means of adjustable 



* It may be iucidentally mentioued that early in 1831, after the satisfactory opera- 

 tion of the first telegraphic magnet, Heury contrived the lirstElectro-magueticE-uginc, 

 comprising an oscillating horizontal electro-magnetic har, just below each end of which 

 ■was secnred an npright permanent magnet, the two having similar poles. The polar- 

 ity of the oscillating electro-magnet Avas reversed at the moment of attractive contact, 

 by automatically inverting the circnit current, and thus each of its poles was alter- 

 nately attracted and rejielled by its neighboring magnet. (Silliman's Am. Journal of 

 Science, July, 1831, vol. xx, pp. 340-343.) Henry was therefore the original inventor 

 of the automatic xiole-chaugcr or commntator, — a device having a very wide range of 

 nseful a])plication. The illustrious English physicist, James P. Joule, in his "His- 

 torical Sketch of the rise au<l progress of Electro-magnetic Engines for propelling 

 machinery," remarks : " Tlie improved plan by Professor Heury of raising the magnetic 

 action of soft iron, developed new and inexhaustible sources of force which ajtpeared 

 easily and extensively available as a mechanical ageut ; and it is to the ingenious 

 American philosopher, that we are indebted for the tirst form of a working model of 

 an engine upou the principle of reciprocating polarity of soft iron by electro-dynamic 

 agency." (Sturgeon's Annals of EJectriciiij, etc. March, 1839, vol. iii, p. 430.) 



t A quarter of a century afterward Henry could proudly say, " I have sought no pat- 

 ent for inventions, and solicited no remuneration for my labors, but have freely giveu 

 their results to the world; expecting only in return to enjoy the consciousness of hav- 

 ing Jidded by my investigations to tlie sum of human knowledge, and to receive the 

 credit to which they might justly entitle me." {Smithsonian llcport for 1857, p. 8u.) 



