In July of last year Professors Runge and Paschen (‘Phil Mag.,' 1895, [ii], vol. 40, pp. 297—302) announced their discovery that the spectrum of the gas from clèveite indicated the presence of two elements. They also stated that by means of a single diffusion through an asbestos plug, they had been able to effect a partial separation of the lighter constituent, which was characterised by the green glow which it gave under the influence of the electric discharge in a vacuum-tube, and which was represented in the spectrum by the series containing the green line, λ = 5015·6. Subsequently, at the meeting of the British Association at Ipswich, Professor Runge exhibited a tube containing the so-called green constituent; the colour of the glow differed strongly from that of an ordinary helium tube, but the gas contained in it was evidently at very low pressure, as phosphorescence was just commencing. Professor Runge has since acknowledged that the green effect in the helium tube may be produced by a change of pressure alone (‘Astrophysical Journal,’ January, 1896).
Some experiments on helium