16 AUGUST 1946, Page 14

"ABOUT THE ATOM"

Sia,—In the issue of August 2nd I regret to say that Professor Dingle has misquoted me on some occasions and has thus misrepresented my meaning. Thus he has objected to the use of " unstable " for the normal electron structure of all gases except rare gases, but has omitted to refer to my note on p. 37 that the word " unstable " is . used in a restricted sense to denote an open configuration. This alters the whole meaning of the term. Again, he credits me with stating that "there is a strict limit to the number of electron orbits in an atom," whereas my actual words on p. 51 axe, "There is a strict limit to the number of orbits in which the electron can move "—an entirely different representation as Professor Dingle will see from the few lines following in which the electron-jumps into different orbits are dealt with. In another part of the review he says, " No human eye can see, nor could the air even transmit, light-waves throughout the range to-•Lio-5 cm." I did not say that this could occur. Having given the wave-lengths of various forms of radiation (only approximately) on p. 53, I said on p. 54 that "the range for visible light is very narrow—from about to-' to to' cm." The actual figures are given on p. so,7 x ro-5 cm. for red light and for

violet light about 3-5 x cm. I am puzzled to know why Professor Dingle should object to my saying that this range is about so' to so' cm. He has obviously missed the relevant word "about." I am very grateful to him for pointing out an unfortunate slip in the use of the word " found " for " produced " or " obtained " on p. 69, though on pp. 106-7 the correct words are used. Perhaps I should have added that Norway was formerly the chief source of heavy water in Europe owing to the cheap supply of hydro-electricity atailable.—Yours faithfully, Holy Trinity Vicarage, Comin; Town, E. 16.

M. DAVIDSON.