344 M. E. Goldstein on Spectra of Gases. 



extends much further at temperatures not particularly high than 

 Wiillner indicates for the state of perfect formation of the con- 

 tinuous spectrum. 



The first spectrum of hydrogen, according to Wiillner, ends 

 between H ft and H 7. I have seen it much further. The strong 

 fluorescence of the glass tubes which the light causes ought to 

 have shown long ago that the spectrum is much longer than has 

 been indicated hitherto. The dispersion of brightness in the 

 continuous ground of many line-spectra seems to me to corre- 

 spond so much with the relative intensity of certain places in the 

 spectrum of the first order, that I tried to get at a continuous 

 spectrum directly from a band- spectrum by raising the tempera- 

 ture. In this I have succeeded very well with nitrogen ; unfor- 

 tunately at present there is no time for a closer investigation of 

 hydrogen in this regard. I do not attach particular importance 

 to a single experiment which confirms my view. 



The spectrum of the second order is obtained with the lowest 

 densities in which jar-discharges still go through a narrow tube 

 filled with air ; these densities are represented by fractions of a 

 millimetre. If, then, while constantly using jar-discharges one 

 lets the density increase, the lines disappear and the band-spec- 

 trum appears. If the density still increases, then the brightness 

 of the dimmer band-parts grows perceptibly faster than that of 

 the stronger maxima ; the proportion of brightness reaches unity 

 as a limit, and successively more and more bands are replaced 

 by evenly illuminated continuous bright parts. I could extend 

 the continuous spectrum (in which the eye, in spite of great 

 brightness of the whole, does not distinguish any single bands) 

 from the red to the violet ; only the most extreme bands at the 

 refrangible end were still distinct. As the formation of conti- 

 nuity progressed in the direction towards the refrangible end, I 

 do not doubt that, with a still more favourable arrangement, even 

 the most extreme part of the spectrum could be obtained per- 

 fectly continuous. The absolute brightness of the continuous 

 spectrum was not so great that a deception caused by excessive 

 intensity of light was possible. If the density be then further 

 increased, the line-spectrum again appears on a ground which is 

 already continuously illuminated. 



I have convinced myself that the phenomenon I have described 

 has no relation to fluorescence. 



The discharge obtains a characteristic colour when the conti- 

 nuous spectrum appears. While it is white for the line-spectrum, 

 rose-coloured for the spectrum of the first order, the light be- 

 comes of a yellowish rosy tint as soon as the continuous spec- 

 trum appears; so that the eye notices the phase in question 

 without spectral apparatus, by mere observation of the tube. 



