23 August 1958
Dr. W. B. Lewis, F.R.S
13 Beach Avenue
Deep River, Ontario, Canada
Dear Dr. Lewis:
I am especially grateful to you for your letter of 17 August, because it is the only one, of the 100 that I have received
so far in acknowledgment of copies of my book that I sent to the writers, in which an effort is made to give me some constructive
I regret that you have found my processes of argument as distasteful as those of Drs. Libby and Teller. I know how great
the temptation is to present only those facts that support one's convictions, and I have been striving to make my presentation
an over-all balanced one. May I ask that you write me in more detail? I have not been able to understand your critical
remarks - that is, it has seemed to me that in general your criticisms are without basis, and it is for this reason that I
should like to have you write to me again.
Let me discuss the statements that you make in the second, third, and fourth paragraphs of your letter, in order that you
may see why I am having difficulty in understanding your criticisms. In the second paragraph you say that the sentence at
the top of page 81 could be transposed. You transform it to read "A very small amount of radiation may do no harm whatever
to a person; but a very small amount of an ordinary chemical poison (e.g. nitrogen mustard) may harm him in such a way as
to cause him to die or to have a seriously defective child."
It seems to me that the first part of your sentence is not true, in the sense in which I was writing on page 81. Geneticists
in general (that is, essentially without exception) agree that the mutagenic effects of radiation are proportional to the
amount, without any threshold.
As to the second part of your sentence, I would say that I do not consider nitrogen mustard an ordinary chemical poison.
I did not want to confuse my argument and expand my book by mentioning the exceptional case of chemical mutagens. That is
the reason that I introduced the adjective ordinary. I feel that it is justified for me to say that a chemical mutagen is
not an ordinary poison.
Moreover, I have significant doubt as to whether a chemical mutagen, in particular nitrogen mustard, has a mutagenic effect
proportional to the dose. There are no significant experiments on this matter, whereas there are significant experiments
for radiation. Moreover, theoretical considerations do not give a clear answer. I have recently been trying to work out
a detailed molecular theory of the mutagenic action of chemical mutagens, and I found that in the theory that looked best
to me I was making use of two molecules of the mutagen, rather than only one. If this theory should happen to be the right
one, then a small amount of a chemical mutagen—I should say a very small amount, to conform to the sentence at the top of
page 81—would have an extremely small effect. An amount one hundredth as great as an ordinary amount would have an effect
only one ten thousandth as great. Consequently I have doubt as to the justification for the second part of your sentence.
However, I contend, in any case, that the presentation that I give on pages 80 and 81 is a good one.
I judge that the second part of your paragraph two depends upon the first part. I do not understand what criticism is involved
in the second part of your paragraph two.
Your third paragraph relates to carbon-14, and you say that it seems to you that my argument is in scientific error. I am
pretty sure that it is not in error. The factors that you mention—the tying up of carbon-14 in trees, and so on, have all
been taken into consideration in my calculation. We have experimental verification of the correctness of the methods of calculation
in the materials-balance calculations made by Libby for cosmic-ray carbon-14. I must, then, reject your statement that there
is an error in my carbon-14 calculations, although if you were to write to me in enough detail for me to understand the basis
of your statement, I should be glad to go over it carefully, because I know that I, like other human beings, am not infallible.
I may say that the way in which my results are obtained has been illustrated by a somewhat simplified calculation published
on the editorial page of the New York Times for 16 May 1958 . Nobody has published any criticism of my communication
of 16 May 1958 to the New York Times, and no one has written any criticism to me. Doctors Kulp, Braecker, and Schulert had
significant reason for criticizing me and pointing out any error that I might have made, in case there were an error, and
their silence is, I think, significant. In fact, I have had two telephone conversations with them (Dr. Kulp), in which
I asked him to point out any error in my calculation, and I have written several letters to these authors, without getting
a reply. In the telephone conversations Dr. Kulp was silent when I asked him about errors in my calculations.
Also, I may say that I have written a detailed paper, about 20 typewritten pages, for publication in Science. Publication
of the paper has been held up, while a referee examined it—carefully, I hope. At any rate, I have now made small revisions
in the wording, in accordance with the recommendations of the referee, which were, in fact, criticisms of my wording. The
referee did not have any criticism of the calculations themselves to make. I hope that my paper on carbon-14 will be published
within another six weeks or two months.
Consequently I have a reasonably strong conviction that you are not justified in saying that my argument about carbon-14 is
in scientific error. Again let me say, however, that I recognize the possibility that it is, and I request that you write
to me again, with a sufficiently detailed discussion of the point to permit me to understand it.
As to your paragraph three, I should like to point out that the ions that are produced by radiation are not of the same type
as those produced by hydrolysis. The latter ions, involving in general often transfer of protein from a molecule such as a carboxylic acid to a water molecule, or the separation of a molecule such as
sodium chloride into sodium ions and Chloride ions, are, of course, not a cause of damage to the human body. However, the
process of ionization by high-energy radiation is one of electronic ionization, in which an electron is removed from a molecule,
leaving an ion that is also a free radical. Ions of this sort do not in general occur naturally (except, of course, as produced
by natural high-energy radiation).
In writing my book I have made an effort to make statements that would give the right impression to the ordinary reader, and
at the same time represent the truth as accepted now by scientists. I have had enough experience in writing to know how difficult
it is to do this, and I have not hoped to have complete success. I am troubled that you have been dissatisfied. If, as I
think to be the case, your dissatisfaction is based upon a misunderstanding of some of the scientific points, I shall not
be so troubled. In any case, I hope to benefit by your further criticism, so that, if a second edition of the book should
ever be published, I might be able to make some improvements.
I shall look forward to hearing from you again.