" THE MID-TWENTIETH CENTURY ATOM "
Sus,—My attention has been called to the Rev. M. Davidson's letter in The Spectator of August 16th stating that, in reviewing his book, The Mid-Twentieth Century Atom, in the issue of August 2nd, I misquoted and misrepresented him. I unaccountably missed this letter at the time or I would at once have pleaded "Not guilty." The first of the three points raised concerns his use of the word " unstable." Mr. Davidson complains that I did not refer to his definition of the word. But it is precisely that definition that I objected to, and I gave the number of the page which he says I missed. If I call Mr. Davidson a pagan philosopher, and define a pagan philosopher as an Anglican clergyman, a critic has the right to object to my diction. My objection here is of that kind, and it is justified by the fact that Mr. Davidson has himself to use the word " stable " more nearly in its proper sense, and not in his own quite different sense, on p. 52, line 9.
Secondly, he states that I make him say there is a strict limit to the number of electron orbits in an atom, when he actually said, " There is a strict limit to the number of orbits in which the electron can move." My statement of his meaning was not in quotation marks, and I see no significant difference between it and his own ; but since he does, I will say that there is no strict limit to the number of orbits in which the electron can move. There are some orbits in which it cannot move, but that is a different thing ; there are still an unlimited number in which it can. Finally, and most surprisingly, Mr. Davidson claims justification for saying that the range of wave-lengths for visible light is " from about so' cm. to to= cm.," when his more exact estimate is 7 x ro-' to 3.5 x ro-' cm. Expressed in the customary units, this- means that he has represented the range 7,000 to 3,500 angstroms by ro,000 to r,000 angstroms, i.e., a twofold by a tenfold range. I have not, as he says, " obviously missed the relevant word ' about '" ; have simply objected to its abuse. He seems to have walked into the most obvious trap lurking in the decimal scale of notation. I have only one amendment to make as the result of Mr. Davidson's letter. In the review I attributed the numerous errors, of which I gave a few examples, to " undue haste." It now appears more probable that they arose from defective under-
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