214 Mr. M. Donovan on the supposed Identity of the Agent 



considerable whirl of the needle took place. In further proof 

 that the whirl of the needle twice round was due to the chemical 

 action of the sulphur on the strip of copper, it is enough to ob- 

 serve, that, on repeating the experiment without the sulphur, the 

 deflection was trifling. 



Two silver wires, treated in the same manner in the flame of 

 a spirit-lamp, one being topped with sulphur, produced momen- 

 taiy deflection of 90°. 



A thin iron wire, connected with the galvanometer, was heated 

 in the Russian furnace, and being touched by a similar iron wire, 

 also connected with the galvanometer, with a particle of sulphur 

 adhering to the point of contact, the needle started off" 183°. 



Some nitric acid in a glass capsule was connected with one of 

 the binding-screws of the galvanometer by a platinum wii-e; 

 another platinum wire was connected with the other ; and its 

 other end twisted into a knob was first dipped into a little 

 spirit of turpentine, and then into the nitric acid ; there was an 

 immediate deflection of 40°. 



An iron wire, maintained at a red heat in a spii'it-lamp, was 

 touched at the point with the point of another iron wire holding 

 a particle of iodine, both vnres being pi'operly connected vnth 

 the galvanometer ; the flame of the lamp became green, and the 

 needle started ofi" 100°. 



A rod of grain tin, heated in the spirit-lamp to its melting- 

 point, was touched with a particle of sulphur on the point of a 

 thin platinum vtdre ; there was a momentary deflection of 56°. 



A thin rod of antimony and a zinc wire were heated in the 

 Russian furnace to the point, when both metals melted at the 

 ends : the zinc wire in melting bent down, but still retained its 

 continuity, and touched the melted drop of antimony still ad- 

 hering ; the needle instantly whirled round entirely. This is a 

 difficult experiment to succeed in. 



A slender rod of antimony was heated in the flame of the 

 Russian fui'nace ; and just as it was in the act of melting at the 

 point, the drop was received on the end of a rod of grain tin also 

 in the act of melting : the needle whirled round. If the metals 

 be not kept free from oxide in these experiments they will fail. 



A ribbon of sheet copper was heated to a bright red in the 

 Russian furnace, and a rod of grain tin was heated at its end to 

 the melting-point ; a drop from the tin was allowed to fall on 

 the white-hot copper, the connexion of the drop with the rod of 

 tin being still maintained ; the needle started off" 130°, and in 

 another trial it traversed the circle entirely. Combination seemed 

 to have taken place superficially, for the copper was whitened at 

 the place of contact. 



It appears to me, that the three last experiments are sufficiently 



