On March 12, Watson sent Delbrück a letter, illustrated with rough sketches, discussing
their new model. He warned his mentor not to tell Pauling about it until they were
more certain of their results, but Delbrück, never one to keep secrets, immediately
passed the letter around. Pauling's mind raced as he read it. He saw immediately that
the Cavendish structure was not only chemically reasonable but biologically intriguing.
"The simplicity of the structural complementariness of the two pyrimidines and their
corresponding purines was a surprise to me-a pleasant one, of course, because of the
great illumination it threw on the problem of the mechanism of heredity," he said.
A few days after seeing Watson's letter, Pauling wrote a colleague, "You must, of
course, recognize that our proposed structure is nothing more than a proposed structure.
There is a chance that it is right, but it will probably be two or three years before
we can be reasonably sure. . . ."