M. Matteucci on the Electricity of Flame. 399 



that the sun should act thus oppositely by his change of 

 declination in these two places and not in the others, limiting 

 itself in these last to only diminishing the fluctuations. It was 

 added, that the changes at St. Helena and at the Cape not 

 having reference to the sun's zenith-distances, his influence 

 ought to be due to an astronomical rather than to a geographical 

 and local cause. It may however naturally be expected that 

 such a period is marked by the many convolutions and superim- 

 positions of difi'erent causes acting on the needle; to extricate it 

 was not easy, and would have been actually impossible without 

 the previous labours of Colonel Sabine, which I have happily 

 found sufficient for the purpose. 



[To be continued.] 



L. On the Electricity of Flame, By M. Matteucci*. 

 My dear Grove, 



IHxiVE gladly taken advantage of a few days' leisure in the 

 country to comply with your request, and at the same time 

 satisfy my own -curiosity, by making some experiments on the 

 electricity of flame, and I now send you the little which I have 

 gathered from my own observations on the subject. I began by 

 studying the conductibility of flame, and employed for this pur- 

 pose a galvanometer constructed by Ruhmkorfi*, similar to that 

 of M. du Bois Reymond, the fine copper wire of which makes 

 24,000 evolutions round a good astatic system. The flame used 

 in most of my experiments was that of a common spirit-lamp_, 

 or of a double current lamp belonging to the laboratory. The 

 circuit, which contained two DanielFs couples, was formed by two 

 platinum wires, two-thirds of a millimetre in diameter, placed 

 horizontally, and leaving between them a fixed interval of 8 mil- 

 lims. All was perfectly insulated, and the flame completed the 

 circuit. On seeking to ascertain the conducting power of the 

 diiferent parts of the flame, it is soon found that this conducti- 

 bility increases rapidly in going from the base or root of the 

 flame towards the summit. To give an idea of this difierence, I 

 mention here that I had from 4° to 5° of deflection at the base, 

 8° to 10° at the middle, and from 30^ to 40° at the upper part 

 of the flame. By placing the platinum wires in the flame of a 

 double current lamp, much more striking efl'ects are obtained, 

 which are evidently in proportion with the temperature of the 

 gas composing the flame. If we hold the platinum wires at a 

 less interval apart, that is, from 2 to 3 millims., over the flame 

 of the double-current lamp, which can be diminished at pleasure, 

 we can ascertain the precise moment at which the conductibility 

 of the flame begins ; I found in my experiments that this moment 

 * Communicated by W. R. Grove, Esq- 



