﻿420 Of the "Electron,'' or Atom of Electricity. 



That determination was made twenty years ago, and is 

 founded on the estimate I had previously announced in 1867 

 of the number of molecules present in a gas, viz.: 10 18 in 

 each cubic millimetre of a gas at standard temperature and 

 pressure (see Phil. Mag. for August 1868, vol. xxxvi. 



An estimate of this same remarkable unit of electricity 

 was made in 1891 by Professor Eicharz, as quoted by Pro- 

 fessor Ebert (see p. 335 of the September number of the 

 Phil. Mag.). His determination mahes the electron = 12*9 

 eleventhets (12'9 x 10 -11 ) of the C.G.S. electrostatic unit, 

 This appears to be in sufficiently satisfactory agreement with 

 my previous determination, having regard to the amounts of 

 the probable errors of some of the data. 



Finally, in 1891 (see Transactions of the Royal Dublin 

 Society, vol. iv. p. 583), I called attention to the fact, which 

 Professor Ebert appears also to have noticed in 1893 (see 

 footnote on p. 335 of the September number of the Phil. 

 Mag.), that the motions going on within each molecule or 

 chemical atom cause these electrons to be waved about in the 

 luminiferous aether, and that in this constrained motion of 

 the electrons the distinctive spectrum of each kind of gas 

 seems to originate : since lines in the spectrum will be fur- 

 nished by each term of the Fourier's series which represents 

 the special motion of each electron (see Transactions of the 

 Royal Dublin Society, vol. iv. 1891, p. 585). In fact the 

 only other conceivable source of these spectra is excluded, 

 viz., Hertzian undulations consequent upon electric discharges 

 within or between the molecules. This is because these 

 undulations, if they exist, must consist of waves of far too 

 high frequency to produce lines that can be visible, or even 

 that could be situated within any part of the spectrum that 

 has been reached by photography — a circumstance to which 

 my attention was called by Professor FitzGerald. They 

 cannot, therefore, be the cause of any part of the hiown 

 spectra of gases. 



I am, Gentlemen, 

 Yours faithfully, 

 8 Upper Hornsey Rise, N. G. JOHNSTONE StOXEY. 



September 4, 1894. 



