" This new instrument was made bv me in the year 1831 and I have already men- 

 tioned this in the fourth part of my first memoir on temporary magnetism which I 

 published in volume VI of the Atti dell' Accademia di Scienze, Lettere ed Arti dt 

 Padova." [The volume number appears to be an inaccurate reference to volume III 

 of Nuovi Saggi, etc. as indicated above.] 



4. Telegraphy 

 In 1831, following the description of the experiments which led to 

 his discovery of the proper proportioning of the battery and the mag- 

 net, Henry stated : 



"But be this as it may, the fact, that the magnetic action of a current from a 

 trough is, at least, not sensibly diminished by passing through a long wire, is directly 

 applicable to Mr. Barlow's project of forming an electro-magnetic telegraph. . . . « 



Henry later corrected this reference to Barlow since Barlow's investi- 

 gation merely tended to disprove the possibility of the telegraph. Bar- 

 low's statement regarding the telegraph was: 



" In a very early stage of electro-magnetic experiments, it had been suggested, that 

 an instantaneous telegraph might be established by means of conducting wires and 

 compasses. The details of this contrivance are so obvious, and the principles on 

 which it is founded so well understood, that there was only one question which could 

 render the result doubtful, and this was, Is there any diminution of effect by lengthen- 

 ing the conducting wire? ... I was, therefore, induced to make the trial, but I 

 found such a sensible diminution with only 200 feet of wire, as at once to convince me 

 of the impracticability of the scheme." '" 



Even as late as 1837, Wheatstone in England had satisfied himself 



by experiment that the development of electro-magnetism in soft iron 



at a distance was impracticable. Cooke had sought to develop 



magnetism at a distance for the purpose of sounding an alarm. His 



experiments were unsatisfactory and on asking advice of Faraday and 



Roget was referred by the latter to Wheatstone. Wheatstone's 



statement was: 



" I believe, but am not quite sure, that it was on the 1st of March 1837, that Mr. 

 Cooke introduced himself to me. . . . Mr. Cooke [later] showed me some of his 

 drawings and models, and though I could not fully comprehend the full scope of 

 them at the time, I saw and understood enough to assure me that his instrument was a 

 massive complicated piece of machinery, intended to be set in action by the attractive 

 power of an electro-magnet. On seeing this, and relying on my former experience. I 

 at once told Mr. Cooke that it would not and could not act as a telegraph, because 

 sufficient attractive power could not be imparted to an electro-magnet interposed 

 in a long circuit; and to convince him of the truth of this assertion, I invited him to 

 King's College, to see the repetition of the experiments on which my conclusion was 

 founded. He came, and after seeing a variety of voltaic magnets, which even with 

 powerful batteries exhibited only slight adhesive attraction, he expressed his dis- 

 appointment in these words, which I well remember, 'Here is two years' labour 

 wasted.' " ^^ 



Henry in 1831 or 1832 at Albany acted on his own suggestion as to 



9 SW. Vol. 1, p. 42. 



1" Edinburgh Philosophical Journal, Jan.-Apr. 1825. 



11 The Electric Telegraph: Was It Invented by Professor Wheatstone?, by W. F. 

 Cooke, Part 2, pp. 86-87. 



11 



