1902.] Dr. J. A. Fleming on the Electronic Theory of Electricity. 163 



WEEKLY EVENING MEETING, 



Friday, May 30, 1902. 



Sir William Crookes, F.E.S., Honorary Secretary and 

 Vice-President, in the Chair. 



Dr. J. A. Fleming, M.A. F.E.S. M.B.L, 

 Professor of Electrical Engineering, University College, London. 



The Electronic Theory of Electricity.* 



Considerable progress has been made of late years in our knowledge 

 concerning the structure and relations of atoms and electricity. 

 Recent discoveries have moreover placed in a new light old theories 

 and experimental work. The remarkable investigations and deduc- 

 tions made from his own experiments and those of others, which 

 have led Professor J. J. Thomson to the conclusion that atoms can 

 be split up into, or can give off, smaller masses, which he calls 

 corpuscles, have been explained by him on many occasions.f There 

 seems to be good evidence that in a glass vessel exhausted to a 

 high vacuum, through the walls of which are sealed platinum wires, 

 we have a torrent of small bodies or so-called corpuscles projected 

 from the kathode or negative wire, when the terminals are connected 

 to an induction coil or electrical machine. 



Twenty-five years ago Sir William Crookes explored with wonder- 

 ful skill many of the effects due to electric discharge through such 

 high vacua, and came to the conclusion that they could only be 

 explained by the supposition that there was present in the tube 

 matter in a fourth state, neither solid, liquid, nor gaseous, but 

 ' radiant matter ' projected in straight lines from the surface of the 

 negative pole or kathode, the particles moving with immense velocity, 

 and all charged with negative electricity. He showed by beautiful 

 experiments that this radiant matter bombarded the glass walls and 

 produced phosphorescence, could be focussed on to metal sheets and 

 render them red hot, and could drive round little windmills or vanes 

 included in the tube. It therefore possesses the quality of inertia, 



* The following pages do not contain a verbatim reproduction of the discourse 

 delivered on this occasion, but are a reprint of an article in the ' Popular Science 

 Monthly,' for May 1902, by the lecturer, covering substantially the same ground, 

 and reproduced here by kind permission of the editor, Professor J. McKeen 

 Cattell. 



t See • Popular Science Monthly,' vol. lix. p. 323, " On Bodies smaller than 

 Atoms," by Professor J. J. Thomson, F.R.S. See also by the same author a 

 paper in the ' Philosophical Magazine ' for December 1899, " On the Masses of 

 the Ions in Gases at Low Pressures." 



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