Intelligence and Miscellaneous Articles. 407 



low temperatures, and vice versa. Thus, at very feeble pressures 

 (0-001 metre), with tubes of oxygen or nitrogen and with very 

 small Leyden jars, we obtain the spectrum which Pliicker attributes 

 to high temperatures, while the tube is scarcely warm after the ex- 

 periment has last several minutes, aud the brilliancy of the light 

 emitted by the incandescent gas is very feeble. The same tube, 

 traversed by the current of a very powerful induction-coil (without 

 the interposition of a Leyden jar), emits, on the contrary, an ex- 

 tremely bright light, becomes rapidly hot, and nevertheless gives 

 the spectrum which Pliicker attributes to low temperatures. 



But here is a still more decisive experiment. Let us take a tube 

 in the form of an H with four electrodes, and filled with nitrogen*, 

 oxygen, or one of those gases (or vapours) which give two spectra. 

 Through this tube let us pass at the same time the currents of 

 two induction-coils, of which one has a Leyden jar interposed. 

 We shall observe the two spectra superposed — the spectrum assigned 

 to elevated temperatures {Leyden jar), and the spectrum assigned to 

 low temperatures (ordinary sparTc). 



According to Pliicker' s hypothesis, the gas would have, at the 

 same physical iustant, two different temperatures, which is inad- 

 missible. 



It may perhaps be objected that, the interrupters of the two coils 

 not working strictly in unison, the perception of the two spectra is 

 due to the persistence of the images upon the retina. But this is not 

 the case, as some tubes, especially with oxygen, give forth light for 

 several tenths of a second after the current has been interrupted. 



We attribute the change in the spectra given by these metalloids 

 to a vibratory state peculiar to their molecules, directly depending 

 upon the nature of the electricity employed. Thus, a tube of 

 highly rarefied hydrogen gas, submitted to the action of ordinary 

 sparks, presents quite a different aspect from the same tube submitted 

 to the action of the condensed spark. 



Highly rarefied gases, traversed by the continuous current of the 

 battery, or by a current interrupted by sparks (induction-coil), pre- 

 sent a dynamical state well known under the name of stratification. 

 But this stratification differs entirely, according as we employ the 

 ordinary spark, the condensed spark, or the continuous current of 

 a battery of very high tension. 



• We shall see in further communications that with each different 

 behaviour of an incandescent gas (alteration in the stratification, 

 colour of the light emitted, &c.) there is always a corresponding 

 modification, and often an entire change, in its spectral lines — an 

 effect assuredlv independent of the temperature. — Comptes Mendus, 

 Sept, 18, 1882. 



ON A THERMOSCOPIC METHOD FOR THE DETERMINATION OF 

 THE OHM. BY G. LIPPMANN. 



It will be remembered that Mr. Joulet employed a calorimetric 



* Nitrogen in the electric arc gives a different spectrum from that given 

 by Geissler's tubes or the spark in air. 



t Reports of the Committee &c, pp. 175-190 (London, 1873). 



