15th June 1953
Dear Sir Harold,
Some time ago I was offered a temporary job in the United States.  As I believe Dr. Perutz has told you, Dr. David Harker, the head of the Protein Structure Project at the Brooklyn Polytechnic New York, wanted someone from this country with experience in X-ray crystallography to work with them, in order to transmit some of the ideas and experience we have acquired here.
This suggestion appealed to me, especially as it would also enable me to work for a while in a new environment, and would help to shake up my own thinking on this difficult problem.  As at that time my future was rather uncertain, I accepted this offer, only stipulating that I should first finish my Ph.D.  I hope to submit my thesis within a few weeks.  Immigraiton visas have been granted to my family and myself, and we plan to sail on the Mauritania on 22nd August.
Meanwhile, Dr. Perutz has suggested that I might return to the Unit here after my visit to the States.  This proposal is very attractive to me, for two reasons.  Firstly, the conditions of work in this Unit are extremely favourable, both in the facilities provided and in its intellectural atmosphere, and it is the obvious choice for anyone wishing to work on the structure of biologically important molecules.  Secondly, the prospect of further employment by the M.R.C. is, in itself, an additional attraction.  I am now 37, and must give serious consideration to my professional future.  As I expect you know, after making one career for myself in the Admiralty, I gave it up at the age of 30, and with the help of the M.R.C. started again, in biophysics, as I believed my interests lay there rather than in making weapons.  I now have to decide whether I should attempt to enter academic life proper.  This would mean, in effect, starting at (or near) the bottom once again, as I have no academic experience at all.  This, as you can imagine, I am most reluctant to do.
Employment by the M.R.C., on the other hand, would allow me to devote all my effort to research, at a time when my thoughts and energies are flowing strongly in this channel.  My scientific interests are primarily biological, and I only work on molecular structure because I believe it to be the key to the really fundamental biological problems.  One can already look forward to the day when we shall wish to use rather more biological techniques to exploit and develop our knowledge of molecular structure.  Thus my future fields of work, whatever they may turn our to be, are likely to be of direct interest to the M.R.C.
Dr. Perutz has suggested, therefore, that I should be given leave of absence from the M.R.C. while I am in the States.  My appointment with Dr. Harker is for one year, at $.450 a month, plus $.1000 towards travelling expenses.  There has also been a suggestion that I might go for a further six or twelve months to Professor Pauling's Laboratory at the California Institute of Technology, but this is still very open.  Our subject is advancing so rapidly that it is difficult to decide at the moment whether this would be a good idea or not, and I suggest that a decision on this should be postponed.
Meanwhile, if you could agree to my further employment by the M.R.C., and a leave of absence of one year, I should be very pleased.  If you would like me to discuss this with you, I could, of course, come to London at any time.
Yours sincerely,
F. H. C. Crick.