510 



Major J. Herschel. 



disturbance is balanced by the torsion of a single wire. This was 

 followed immediately by a reclamation by Principal Forbes, on belialf 

 of Broun (absent in India), drawing attention to the prior publication, 

 and saying that the new design is practically identical with, that 

 already published. In May of the same year appeared a letter from 

 Broun to the Editors of the "Philosophical Magazine," enclosing 

 translation of a letter from himself to the Perpetual Secretary of the 

 Paris Academy of Sciences, the object of which is likewise to claim 

 priority of invention. He refers to his paper in the Edinburgh 

 " Proceedings " in proof. The whole question turns, I think, on this 

 sentence : — " We found, however, that the spring, like the balance- 

 spring of a watch, employed under the weight, acted badly, and I 

 substituted a simple gold wire in the same year" [1861]. Compare 

 this with the statement in the letter of 1879, where he says 

 " Babinet's proposal was for the same instrument exactly, and it was 

 published more than two years after mine, and after, indeed, I had 

 described the instrument to different persons in Paris." It is clear 

 that Broun did not perceive that there was a real difference between 

 the two forms in which the elasticity of metal was opposed to the 

 force of gravity, and that he had published nothing regarding his use 

 of the torsion wire at the time of Babinet's design. It was only 

 towards the close of 1861, at the earliest, that Broun introduced the 

 gold wire in place of the spring, and as the letters which I shall give 

 prove Babinet to have been working out the same idea early in 1862, 

 there is no doubt some show of reason in Broun's complaint, when he 

 says (as lie does in his letter of 1863) that not only was his instru- 

 ment seen by many persons in Adie's shop in 1861, but that the gold 

 wire whicli he substituted was actually recommended and supplied by 

 a Parisian artist. Still I think it impossible to read the following 

 letter, and retain any suspicion that Babinet was conscious of having 

 borrowed the principal part of his design from another. The letter is 

 interesting enough in itself, apart from this question. 



" Paris, ce 3 Fevrier, 1862. 

 " Sur la Mesure statique de la Pesanteur. 

 "Monsieur et illustre Confrere, 



" C'est une des plus importantes idees qui aient ete emises pour la 

 connaissance de notre globe que celle de la mesure statique de la 

 pesanteur. Je crois avoir resolu le probleme pratique apres d'innom- 

 brables essais et bien des annees de reflexion. Ce qui distingue 

 surtout ma methode, c'est le fractionnement de la pesanteur, de 

 maniere a eqnilibrer l'effet d'un poids considerable par la torsion d'un 

 fil metallique de force moyenne et restant dans les limites de i'elas- 

 ticite parfaite. En eff'et je reduis le poids a de sa valeur au 

 rnoyen du pendule bifilaire. 



