384 Intelligence and Miscellaneous Articles. 



keep the eyes shut whilst the discharges are going on, and only to 

 open them immediately afterwards, so that the retina may not be 

 impressed at the moment of the passage of the electricity. The part 

 of the tube in which the discharge takes place must be at least 15 

 to 20 centims. in length. 



The peculiar action which illuminates the tube takes place between 

 the actual molecules of the oxj'gen gas, and does not pass along the 

 walls of the tube ; for by making use of spheres of a capacity of 

 200 to 300 centims., the entire mass of the gas becomes opaline. 

 Ky prolonging the tubes beyond the platinum wires, it also appears 

 that the rarefied oxygen beyond the part which directly receives the 

 discharge, gives rise to an emission of light. On the other hand, 

 this opalescence of the gas indicates that the effect does not result 

 from electrical discharges due to the electrization of the glass, and 

 which would traverse the space illuminated after the cessation of 

 the inductive discharge, as it may be produced by friction of the 

 outside of the tube. 



When a tube is to give rise to an effect of persistent luminosity, 

 there is produced, at the moment of the passage of the electricity, 

 a yellow tint, which illuminates the mass of gas in the tube, and that 

 independently of the different tints of the electric rays due to the 

 intermixed gases; when this yellow tint disappears, the effect of per- 

 sistence entirely ceases to be appreciable. It is even possible that 

 gases mixed with oxygen may augment the duration of the per- 

 sistence ; for tubes, prepared apparently in similar conditions, fur- 

 nished variable results as to intensity and duration. 



If we operate with a small tube containing rarefied oxygen, after 

 the electricity has passed for some time, the effect of persistence 

 ceases to be appreciable ; this result appears to show that the pecu- 

 liar property in question disappears in the gas at the end of some 

 time. Is it connected with the formation of ozone, which, in a 

 determinate volume, cannot exceed a certain limit ? This I have 

 been unable to ascertain. 



Sulphurous-acid gas sometimes presents an action analogous to 

 that of oxygen ; but the effect not being always exhibited, I have 

 thought that it might depend on a partial decomposition of the gas 

 and on a mixture of oxygen ; the same is the case with rarefied air 

 in the presence of phosphorus. However, I am at present follow- 

 ing out these researches, and hope to ascertain, by means of an 

 arrangement analogous to that which I have employed in the phos- 

 phoroscope, whether other gases and vapours besides oxygen would 

 not give rise to effects of luminous persistence of shorter duration 

 than that observed with the latter. 



Tlie phsenomenon presented by oxygen, and perhaps in different 

 degrees by other gases, probably depends on a peculiar action pro- 

 duced by electricity ; for solar light, and even electric light itself does 

 not give rise to any phosphorescence of this kind. Is it the result 

 of vibrations impressed upon the molecules of the gases, or of a 

 peculiar state of electrical molecular tension persisting for a few 

 moments, or of some other physical or chemical cause? — Comptes 

 Rendus, Fedruary 21, 1859, p. 404. 



