THE text of J. J. Thomson‘s historic Royal Institution lecture of April 30, 1897, on “Cathode Rays”, has been reproduced in full in the November-December issue of the American Journal of Physics as the contribution of the American Association of Physics Teachers to the Electron Jubilee celebrations (see also Nature, 160, 776 ; 1947). 

It will be recalled that it was in this lecture that J. J. Thomson, after discussing Lenard‘s, Perrin‘s and some of his own experiments on the charges carried by cathode rays, concluded that "the size of the carriers [of electrical charge] must be small compared with the dimensions of ordinary atoms and molecules". Further, that from his experiments on the deflexion of cathode rays, he was able to deduce a value for m/e which, quoting from the final words of the lecture, was “of the same order as the value lO-7 deduced by Zeeman from his experiments on the effect of a magnetic field on the period of the sodium atom”.