48 Mr Waran, The effect of a magnetic field 



leaving the hydrogen lines comparatively unaffected, so that by a 

 casual examination of the spectrum the hydrogen and the neon 

 lines can be distinguished from one another. 



The oxygen spectrum is rather difficult to excite when mixed 

 with other gases. Yet a mixture of hydrogen, oxygen and a trace 

 of helium was tried with success and here again the monatomic 

 helium lines were brouglt out by the magnetic field, leaving the 

 diatomic oxygen and hydrogen lines comparatively unaffected as 

 shown in the photographs. 



From these experiments the natural inference follows that in 

 a mixture of the monatomic and diatomic gases, the monatomic 

 gases alone seem to be selectively affected in a peculiar way 

 resulting in their spectrum lines alone being very considerably 

 enhanced or brought out prominently even when not visible at 

 all previously. By this method minute traces of the monatomic 

 gases when mixed with other diatomic gases can be detected. 

 On this view we might also explain the abnormal mercury line 

 6152 and others as due to the radiation from the monatomic 

 atom while the other lines may be classified as belonging to the 

 molecule. 



Examining the spectrum of the atmospheric air at low pressure 

 in this way the effect of the magnetic field is to bring out new lines 

 which are not present without the magnetic field, as shown in the 

 photographs. As far as their wave lengths have been determined, 

 though one or two of them fit in fairly well with lines catalogued 

 as belonging to oxygen and nitrogen, yet there are others which 

 are difficult to identify while the absence of other stronger lines of 

 oxygen and nitrogen make even these two or three fits inconclusive. 



Another interesting point noted in these experiments is the 

 varying degrees of enhancement under the influence of the field 

 for lines belonging to the same element helium. Preston has 

 shown that the Zeeman effect is of the same magnitude for lines 

 belonging to the same series, but differs in different series. Simi- 

 larly we might expect the degree of enhancement of the lines in 

 the magnetic field to depend on the series to which the line belongs. 



The exact nature of this phenomena and the mechanism of the 

 reaction that brings about these novel changes in the general 

 spectrum is not yet definitely known and it is not desirable to 

 attempt an explanation until the study of the spectrum has been 

 extended to the ultra violet. 



The current in the tube was usually about 3 m.a. and the effect 

 of the field was to decrease the current by about 20 to 30 per cent. 

 The changes of intensity observed cannot be attributed to this 

 since the reduction of the current by a spark gap in series only 

 brings about a proportionate decrease in brilliancy of the general 

 spectrum. 



