PHENOMENA RELATING TO THE SPECTRA OF HYDROGEN AND HELIUM. 253 
The Sharp series of Helium, AA7065, 4713, 4121 exhibits the transfer in a more 
normal manner. As regards central intensity alone, A7065, while giving a definite 
trace on the wedge photograph in the ordinary spectrum, cannot be detected on the 
corresponding photograph with the condensed discharge. A4713 is enhanced in the 
ratio 1‘20, and A4121 in the ratio 1 '99, which is much greater. At the same time, 
each of these two lines is considerably broader, so that the enhancement of their 
energy-content is very great. The Principal line A3888 is slightly broadened by the 
condensed discharge, and its central intensity is reduced to 0'7. Again no conclusion 
can be drawn without another line for comparison. 
The Diffuse Parhelium series, AA6678, 4922, 4388 is enhanced in the ratios 1‘50, 
1‘355, 2'82. Both the Diffuse series are relatively enhanced with the condensed 
discharge. The lines become progressively broader towards the violet, so that the 
energy-enhancement of A4388 is very great in comparison with that of A6678, and 
that of A4922 exceeds that of A6678 when its breadth is taken into account. 
In connection with the nebular spectrum, it is interesting to notice that AA4472, 
4388, 4026 are enhanced by the condensed discharge to an abnormal extent in 
comparison with any other lines, and their increase of breadth makes the effect 
more conspicuous. 
The Sharp series of Parhelium is normal, for A5047 is not visible through the wedge 
in either case, and A4437 only with the condensed discharge. For the Principal series, 
A5015 is reduced to y^, whereas A3965 is enhanced to -V~,—’again a normal effect. 
The broadening with decreasing wave-length is, although definite, much less striking 
in these series, and its most pronounced effects occur in the two Diffuse series. 
The transference of energy of emission to the higher members of the series is 
actually much greater with the condensed discharge than in the bulb, although it is 
not so strikingly apparent owing to the broadening of the Diffuse series, which are 
the most affected. 
The fundamental importance of a phenomenon of this type is perhaps a sufficient 
justification for exhibiting the results derived from a third plate—in which all the 
three spectra are present together. The height of the wedge in the enlargement 
is 34 mm. for the condensed discharge and 33 for the others. 
The first two columns of ratios are again in general agreement with the phenomenon 
already established, and more especially when the breadths of the lines on the plate 
are taken into account. There is, in fact, no case of exception. But other important 
facts are brought out in this table. In the first place, the stage of energy transfer in 
this experiment is not quite the same as before, and it therefore depends on the 
circumstances of the experiment—perhaps on the pressure of gas and so on, and 
further work is required in order to test the possibility of transferring the energy 
further down the series. For one very interesting question which is raised is the 
possibility of transferring all the energy into the final members, so that the series 
would ultimately behave like a band so far as it is visible. But if this be possible, 
2 N 
YOL. CCXYII.-A. 
