432 WRITINGS OF JOSEPH HENRY. [1857 



magnetic machines which have since exercised the inge- 

 nuity of inventors in every part of the world, and were of im- 

 mediate applicability in the introduction of the magnet to 

 telegraphic purposes. Neither the electro-magnet of Sturgeon 

 nor any electro-magnet ever made previous to my investiga- 

 tions was applicable to transmitting power to a distance. 



The principles I have developed were properly appreci- 

 ated by the scientific mind of Dr. Gale, and applied by him 

 to operate Mr. Morse's machine at a distance.f 



Previous to my investigations the means of developing 

 magnetism in soft iron were imperfectly understood. The 

 electro-magnet made by Sturgeon, and copied by Dana, of 

 New York, was an imperfect quantity magnet, the feeble 

 power of which was developed by a single battery. It was 

 entirely inapplicable to a long circuit with an intensity bat- 

 ter}', and no person possessing the requisite scientific knowl- 

 edge, would have attempted to use it in that connection 

 after reading my paper. 



In sending a message to a distance, two circuits are em- 

 ployed, the first a long circuit through which the electricity 

 is sent to the distant station to bring into action the second — 

 a short one, in which is the local battery and magnet for 

 working the machine. In order to give projectile force suf- 

 ficient to send the power to a distance, it is necessary to use an 

 intensity battery in the long circuit; and in connection with 

 this at the distant station a magnet surrounded with many 

 turns of one long wire must be employed to receive and 

 multiply the effect of the current enfeebled by its transmis- 

 sion through the long conductor. In the local or short cir- 

 cuit either an intensity or quantity magnet may be employed. 

 If the first be used, then with it a compound battery will be 

 required ; and therefore on account of the increased resist- 

 ance due to the greater quantity of acid, a less amount of 

 work will be performed by a given amount of material ; and 

 consequently though this arrangement is practicable it is by 

 no means economical. In my original paper I state that the 

 advantages of a greater conducting power, from using sev- 



t [See Appendix A, at the end of this paper.] 



