20 April 1953
Professor Max Delbruck
California Institute of Technology
I received your letter, to Harry Weaver, this morning, and immediately telephoned him.
He had not seen your letter yet, but after I told him what you had said, and what my opinion was, he said that he would bring
Watson over for the Virus Symposium.
He suggested that they might save money by having Watson stay here through the summer, instead of returning to England.
I pointed out that the work that Watson is doing in collaboration with Crick is very important, and that it might well be
important enough to justify sending him back to Cambridge, even for the period of two months. I judge that he agreed to
do that, if necessary.
I was very deeply impressed by the Watson-Crick structure, I do not know whether you know what put Corey and me off on the
wrong track. The x-ray photographs that we had, which had been made by Dr. Rich, and which are essentially identical with
those obtained some years ago by Astbury and Bell, are really the superposition of two patterns, due to two different modifications
of sodium thymonucloates. This had been discovered a year or more ago by the King's College people, but they had not announced
it, and I did not know that this was so. Corey and I had tried to find the structure that accounted for one of the principal
features of one pattern, and simultaneously for one of the principal features of the second pattern, Watson and Crick saw
the x-ray photographs made in King's College a couple of months ago, when they attended a seminar there, and they immediately
began work on the problem. The King's College people had already derived one conclusion from the photographs, as to the
nature of the helical structure. Watson and Crick amplified this by the idea of complementariness between purine and pyrimidine
residues, and formulated
Professor Max Delbruck 20 April 1953
their structure. While there is still a chance that their stricture is wrong, I think that it is highly probable that it
is right. It has very important implications, as you mention. It think that it is the most significant step forward that
has been taken for a long time.
cc: Professor Robert B. Corey