THOMSON'S METHOD OF CHEMICAL ANALYSIS 65 



As regards the very special interest and possibilities of the 

 method, in the first place the sharpness of the parabolas 

 obtained, which appears to be only limited by the possible 

 fineness of the canal-ray tube, is the first rigorous and direct 

 proof of an article of scientific faith wjhich has been accepted 

 during many years past without hesitation, namely, that the 

 individual molecules of any given substance all have identi- 

 cally the same mass. 



The point which will probably appeal most strongly to 

 the imaginative mind is that connected with the almost incon- 

 ceivably short time necessary for a particle to exist in order 

 to register its mass. For since a moderate velocity for the 

 positive rays is 10 s cm. per second and 10 cm. is amply sufficient 

 for them to gain their velocity and be deflected by the fields, 

 compounds which have an existence of but the ten-millionth 

 part of a second will infallibly be weighed on this impalpable 

 balance. Hence it is that we need not be surprised at finding 

 upon the plates lines corresponding to molecules found neither 

 in the heavens above nor the earth beneath ; nor need those 

 of us who are chemists hold up our hands in horror at such 

 unnatural and grotesque monsters of the world of molecules 

 as H 3 , CH, CH 2 , CH 3 , N 3 , etc., etc. Rather should we look 

 forward to this line of investigation as an extremely hopeful 

 field in which to study the actual mechanism of dissociation, 

 ionisation and chemical interaction. The method is applicable 

 to the most microscopic quantities of a substance at disposal. 

 That it has already yielded interesting results will, I hope, 

 be apparent from this very brief account ; there seems to be 

 little reason to doubt that, as year by year the technique of the 

 experiments is improved, results of equal and greater importance 

 may be expected from it. 



