344 Prof. W. N. Hartley. On l'</>//on* observed [Apr. 1! 



senting about 1/15 ampere. In two hours and a half the hydrogen 

 introduced into the gas would be about 70 c.c., sufficient, if retaim-d, 

 to reduce the weight by about 4 per cent. The fact that there was no 

 sensible reduction proves that the hydrogen was effectively remove 

 by the copper oxide. 



The nitrogen, obtained altogether in four ways from chemical com- 

 pounds, is materially lighter than the above, the difference amountii 

 to about 11 mg., or about 1/200 part of the whole. It is also to 

 observed that the agreement of individual results is less close ii 

 the case of chemical nitrogen than of atmospheric nitrogen. 



I have made some experiments to try whether the densities * 

 influenced by exposing the gas to the silent electric discharge. 

 Siemens tube, as used for generating ozone, was inserted in the patl 

 of the gas after desiccation with phosphoric anhydride. The follow 

 ing were the results : 



Nitrogen from Air by Hot Iron, Electrified. 



January 1, 1894 2'31163 1 M < 



January 4, 1894 2-30956 / 



Nitrogen from N 2 O by Hot Iron, Electrified. 



The somewhat anomalous result of January 1 is partly explain 

 by the failure to obtain a subsequent weighing of the globe empty, 

 and there is no indication that any effect was produced by the el 

 fi cat ion. 



One more observation I will bring forward in conclusion. Nit 

 prepared from oxygen and ammonia, and about one-half per cen 

 lighter than ordinary atmospheric nitrogen, was stored in the glo! 

 for eight months. The globe was then connected to the apparatus, 

 and the pressure was re-adjusted in the usual manner to the standard 

 conditions. On re-weighing no change was observed, so that the 

 abnormally light nitrogen did not become dense by keeping. 



II. " On Variations observed in the Spectra of Carbon Elec- 

 trodes, and on the Influence of one Substance on the 

 Spectrum of another." By VV. N. HARTLEY, F.R.S., Roya 

 College of Science, Dublin. Received January 13, 1894. 



In a recently published paper by Eder and Valenta, on the " 

 Spectrum of Elementary Carbon and the Ultra-violet Spark S 

 trum of Wet and Dry Wood Charcoal " (Vienna, ' Akad. Wiss. Dent 

 schriften,' vol. 60, 1893), there occurs this passage : 



