MODELS OF POSITIVE ION 315 



carbon, that the spectrum depends upon whether the 

 ion or atom that is radiating carries a positive or 

 a negative charge. 



In the present case, we think it is the positive 

 unstable atom of oxygen that is the chief factor 

 in the production of the continuous or band spec- 

 trum of the negative glow. 



We know, as Schuster has observed, that the 

 spectrum of the negative glow is made up of 

 three parts, namely, the high temperature spec- 

 trum of oxygen, the spectrum of the positive 

 pole, and the continuous or band spectrum. The 

 spectrum of the positive pole would seem to be 

 that of the negative atoms of oxygen, and the 

 band spectrum of the negative glow that of the 

 positive. 



Models of the Atomic Nuclei 



It was with the endeavour to arrive at a 

 comprehensive hypothesis which should form the 

 basis of a mechanical model, by analogies, and by 

 the sifting of facts already within our knowledge, 

 as well as by the results of experiments suggested 

 by these analogies, that this work was undertaken. 

 But it was not, as might indeed have been anti- 

 cipated, without successive failures that the theory 

 which forms the substance of this book has been 

 found to be, so far, the fittest to survive, and 

 been adapted, but only after a direct appeal to 

 Nature in many instances had been satisfied. 



It will help to clear the ideas if we were to 



