330 HENRY AND THE TELEGEAPH. 



mea.sni'ing the quantity of tlio galvanic current by its decomposing energy.* Dr. 

 Schweigger, iu a notice of this paper, remarked that he had previously measured 

 the battery force by the quantity of gases evolved from water iu a given interval, t 

 These experiments likewise, have evidently no relation to the present use of the term 

 "Galvanometer." 



. Nine years earlier than this however, (or six years before Schweigge-r's needle elec- 

 trometer, ) the galvanic dellection of the magnetic needle had been distinctly observed 

 and accurately recorded. For more than a century, repeated endeavors had been made 

 to discover some relation between the magnetic and the electric attractions and repul- 

 sions, or to unite them by a single law. In 1774, a prize was otfered by the Academy 

 of Bavaria for the best examination of and dissertation on the question, " Is there a 

 real and physical analogy between electric and magnetic forces ?" Professor J. H. Van 

 Swiuden, of Fianeker, Holland, one of the successful competitors, supported the con- 

 clusion that the similarities were entirely superficial, and that the two powers were 

 essentially difterent in kind. On the other hand, Professors Steiclehuer and Hubnor 

 contended that analogies so curious must imply a single agent, i 



But the true reaction between these agencies could not well be exhibited initil after 

 1800, when Volta devised his galvanic battery ; which for the first time enabled physi- 

 cists to employ a continuous electric current. Gian Domenico Eomagnosi, a native of 

 Northern Italy, a celebrated publicist and author of several works on historical, legal, 

 and political i)hilosophy, was led near the close of the last century to occupy himself for 

 several years with scientific investigations. The electrical problem attracted his at- 

 tention, and after varied experiments with the aid of the new galvanic appliance, 

 his versatile activity was partly rewarded ; he being first of physical inquirers to make 

 the capital discovery of the singular directive influence exerted by the galvanic cur- 

 rent on a magnetic needle. This new phenomenon — of which he could not anticipate 

 the importance or the consequnces, was announced iu the "Gazzdttadi Trento" of 

 August 3, 1802, an Italian newspai^er published at Trent, in which city he had for 

 many years resided. § If the channel of publication for a contribution to science of 

 such value was unfortunate, the account was at least republished in forms better suited 

 to arrest attention from the learned. 



In a work of some note and merit, entitled "Essai Tb^oretique et Experimental sur 

 le Galvanisme," by Prof. Giovanni Aldini (a nephew of Galvani), quarto, published at 

 Paris in 1804, the author, at page 191, alluding to the supposed magnetic influence of 

 a galvanic circuit, states, ' ' This new property of galvanism has been confirmed by M. 

 Eomanesi, a physicist of Trent, who has observed that galvanism produces a declina- 

 tion of the magnetic needle." This work was republished shortly afterward iu two 

 volumes octavo. 



In the " Bibliotheque Universelle" (Sect. Sciences ei Arts), January, 1821, (shortly 

 after Oersted's announcement,) at page 75, attention is called to Aldini's Treatise on 

 Galvanism, and the passage above given is quoted. The same notice and citation are 

 also juiblished in Gilbert's "Annalen der Physik," 1821, vol. Ixviii, page 208. 



* BihUothcqm Britanniquc, for February, 1811, vol. xlvi. 



t "On a Galvanometer." Schweigger's Journal filr Chemie und Physik, 8vo, Niimberg, 

 1811, vol. ii, part 4, pp. 424-434. 



t Notwithstanding the plausil)ility of this supposition, it remains to the present day 

 Entirely unconfirmed. The conclusion of Van Swiuden was correct. The only approach 

 to a closer analogy since obtained, is the remarkable fact discovered by Amjiere 

 in 1820, that two insulated wires, Iree to move, through which electricity is flowing 

 in the same direction, attract each other like two dissimilar magnetic poles ; and that 

 they repel each other when their currents are reversed, like two similar magnetic poles. 

 But the ditt'erences between tiiese forms of attraction are still so radical, as to incline 

 some physicists to the opinion that the one (that of magnetism) is inherent and in- 

 destructible, and the other (that of electricity) is a mei'ely kinetic or dynamic j)he- 

 nomeuou : while others would regard the two as both kinetic. 



^ Eomagnosi was chief-justice at Trent, from 1791 to 1794 ; and in December of 1802, 

 not long after his scientific achievement, he was made professor of law in the Uni- 

 versity of Parma. 



