82 ON ALLOTROPIC FORMS OF CARBON. 



tically sealed. In this way, and in this way only, was it 

 found possible to obtain a pure spectrum of oxygen. 

 After the connexion with the pump had been made, the 

 whole tube was exhausted, and then the substance con- 

 tained in the hard glass tube was heated. The oxygen 

 which is given off was then removed by the pump, the 

 tube filled a second time with oxygen, this again removed, 

 and this process repeated over and over again, until at last 

 no other lines but those of oxygen are seen when the 

 spark from an induction-coil passes between the electrodes 

 {g and h) . 



When this stage had been reached, and when especially 

 no trace of the carbonic oxide bands could be seen in the 

 tube, the platinum spiral [e] containing either the diamond 

 or the graphite was rendered incandescent by means of an 

 electric current. 



The spiral contained sometimes a piece of natural 

 graphite, sometimes a Cape diamond; but the result was 

 the same in the two cases. As soon as the. platinum 

 spiral had been sufficiently heated, a channelled-space 

 spectrum appeared in the capillary part of the tube. This 

 channelled-space spectrum was carefully compared with 

 the spectrum of carbonic oxide obtained from charcoal 

 and found to be identical with it. No band or line could 

 be seen in the tubes thus prepared which was not also 

 seen in a tabe containing carbonic oxide. The spectrum 

 which appears when a Ley den jar is introduced into the 

 circuit is different ; but here also we found that every line 

 was due either to oxygen or to carbon. Two lines were 

 seen in the green and greenish yellow which are not con- 

 tained in any map of the spectrum of carbon or of oxygen, 

 lines which had not been seen m a great many oxygen 

 tubes prepared and examined by one of us. But it was 

 found on further investigation that these are really 



