Intelligence and Miscellaneous Articles. 325 



was a dark interval, then the repetition of the same effects in the 

 green, and finally in the violet. 



In brief, the spectrum is composed of four grooved portions, in 

 the red, yellow, green, and violet, so identical that they might be 

 taken, except the colouring, for one and the same design which had 

 travelled from the red to the violet. It is quite probable that they 

 obey one and the same harmonic law, which remains to be discovered. 



Of these four regious the green is the most luminous ; it is that 

 which gives the special tint taken by the arc and colouring all 

 objects green. 



During the manifestation of these appearances a chemical action 

 takes place. If any air has been left in the receiver, or if the appa- 

 ratus is not quite closed, the bisulphide of carbon undergoes incom- 

 plete combustion, a mist of sulphur fills the space and is deposited 

 on the sides ; the carbon burns alone. If the air has been well 

 purified, the mist does not form ; a brown deposit settles on the 

 sides, becomes black, sticks to the glass, and tarnishes it. This 

 deposit is volatile ; its odour reminds one of that of sulphur. 



It is evidently a compound of sulphur and carbon, perhaps a 

 protosulphide corresponding to the oxide of carbon, perhaps an 

 isomeric modification of the ordinary sulphide. In fact, neither a 

 deposit of sulphur nor one of carbon is seen, and the carbons of the 

 burner have neither lost nor gained any thing. It is probable that 

 the bisulphide of carbon is dissociated, the sulphur volatilized, the 

 carbon in vapour disseminated in the arc, and that this carbon and 

 this sulphur recombine in the flame to reconstitute a combination 

 under different conditions. But this is only a conjecture, no ana- 

 lysis having yet been made. 



To recapitulate, this experiment is remarkable for the extraordi- 

 nary quantity of light produced, the magnitude of the arc, its 

 colour, the composition of its spectrum, and the chemical actions 

 which take place. It is not likely that it can ever be turned to 

 account for lighting, on account of its colour, unless perhaps for 

 light-houses or distant signals. — Convptes Eendus de VAcademie 

 des Sciences, July 3, 1882, t. xcv. pp. 6, 7. 



ON THE ELECTRIC RESISTANCE OF GLASS AT LOW TEMPERATURES. 

 BY G. FOUSSEREAU.' 



The method employed consists in passing the electricity supplied 

 by a Volta's pile of from 1 to 100 elements across a reaction-tube 

 of 1-2 centim. diameter and very regular thickness, closed at one 

 end. The electricity is collected in a condenser of known capacity, 

 the two armatures of which are connected with the two mercuries 

 of a Lippmann electrometer of measured capacity. The time ne- 

 cessary for communicating to the mercurial column of the electro- 

 meter a displacement corresponding to a determined difference of 

 potential is observed. 



The reaction-tube dips into a wider test-tube ; and its two faces 



