on the intensity of spectrum lines 



431 



field effects are observed similar to those obtained with the dis- 

 charge going transverse to the field. With a leyden jar in parallel 

 with the coil and a spark gap in series with the tube shunted across 

 the condenser, at low pressures the stream-Hke character of the 

 discharge is lost and the discharge passes through the whole section 

 of the tube without seeming to suffer any visible change in the 

 cross-section. But the spectroscopic changes observed are similar. 

 The fact that in many cases the change over the spectrum is 

 brought about practically instantaneously on the application of 

 the field is also against the possibility of any progressive changes 



Fig. 5. 



resulting from the absorption or liberation of some of the component 

 gases. 



There is at times a great similarity between the effect produced 

 by the condensed discharge through the tube and that brought 

 about by the magnetic field, and from that, though we may conclude 

 that the magnetic field brings about a similar violent excitation of 

 the spectrum in some way, we cannot as yet go so far as to say 

 that their effects are identical. For there are important differences 

 between the effects produced by the two. Experimenting with 

 hydrogen the effect of a condensed discharge is found to be mainly 

 to broaden the hydrogen Balmer series lines, especially those towards 

 the violet, where as the magnetic field under the same conditions 



VOL. XX. PART IV. 



28 



