112 ANNUAL OF SCIENTIFIC DISCOVERY. 



of light, one long and the other short, and by celipses of three lengths or 

 durations, lie proposes to obtain the light either 1'rom a Biinscn buttery of 

 fifty elements, or from a magneto-electrical machine, and gives a preference 

 to the latter, as the charcoal points are equally consumed, which is of conse- 

 quence when a lens is employed to concentrate the rays. 



VELOCITY OF ELECTRICITY. 



M. M. Guillemin and Burnouf, of France, have recently instituted an ex- 

 tensive series of experiments on the transmission of electricity by telegraphic 

 wires, with a view of discovering some law which governs its transmission. 

 They conclude from their researches that the electric fluid is not propagated 

 like the waves or undulations of light, and that it has not a constant and 

 uniform velocity. They find it necessary to fall back upon the idea of Ohm, 

 expressed in 1827, that electricity is propagated through wires, in virtue of 

 the same kind of laws which govern the propagation of heat in a metallic 

 bar. To determine experimentally which of these two opinions ought to 

 prevail, that is, whether electricity is propagated with a constant and uni- 

 form velocity, or whether it is transmitted like heat, the authors disposed 

 an apparatus, showing the intensity of the electric current in a certain point 

 of a conducting wire, at different instants of its propagation. The first or 

 the second opinion would then be justified, according as the current acquired 

 suddenly in this point its definite intensity, or arrived at this intensity grad- 

 ually. The authors found that the current at the point in question began 

 with a very feeble intensity (the galvanometer marking 50'), which aug- 

 mented gradually, and soon attained a maximum, which it did not surpass, 

 however long the contact of the pile with the conducting wire was continued. 

 This maximum or permanent, state was obtained in 0'024 of a second of time 

 (the galvanometer then marking 19 50'), in four lines of different lengths. 

 The experiments were made during very fine weather, from 10 to 12 o'clock 

 at night, from the 4th to the 6th of October, 1S59, on a telegraph circuit of 

 104 leagues in length, passing from Nancy to Strasbourg, Malhouse and 

 Vesul, back to Nancy. 



ANALYSIS OF INDUCTION SPARKS. 



M. Moncel, of France, affirms, as the result of his experiments, that the 

 induced spark is not homogeneous, but consists of the original discharge, 

 and of a secondary discharge through a luminous atmosphere, which is 

 generated by the heating and ratification of the adjacent air. He also states 

 that the discharge through this luminous atmosphere exhibits the most 

 striking calorific effects ; while the original discharge possesses the proper- 

 ties of frictional electricity. By employing a microscope to examine the 

 induction spark, he satisfied himself that the luminous atmosphere was only 

 a miniature representation of the induction light seen in a vacuum ; con- 

 tinuing his investigations, he succeeded in detecting in the luminous atmos- 

 phere which accompanies the spark when the discharge takes place in 

 common air, the stratifications which are so remarkable in the hydrogen 

 vacuum. In this experiment he caused the discharge to traverse the flame 

 of a wax candle, when the light of the negative pole, instead of being blue, 

 as in the hydrogen vacuum, was a brilliant Avhitc, owing to the presence of 

 carbonaceous particles. When one of the rheophores is plunged into water, 



