19th May, 1955
Dear Dr. Caspar,
Many thanks for your two letters and diagrams.  I'm very interested in your work, and look forward to having a copy of your thesis.  I shall be particularly interested to know more about what led to your present choice of signs.  As you will know for my letter to Jim, my choice of signs, paste on the existence of a helical groove, is slightly different.  A paper about this is still in preparation, and I'll send you a copy when it's ready.
It would be nice to have you working here for a few months, although I am afraid you will find that we have very little to offer in the way of facilities and space.  However, Jim will be able to tell you something about the sort of conditions in which we work here, and if that doesn't put you off we shall be very glad to have you.  I'm not sure what to understand by "late summer", but I shall be away from the whole of August (first the Brussels conference, then a holiday), and immediately on my return I expect to have two new people to look after, so it would  be best if you would arrive some time in the middle of September.  If that is too late, near the beginning of the month would be possible.
Thank you for the offer of the Pb-TMV.  If anything comes of the work with the I-TMV I certainly think it would be worth while looking at both by both methods. Preliminary results with the I-TMV suggest that said that the change might be similar, I'll let you know more when I've made some measurements.
I enclose the print you ask for.
I hope to be able to send you some manuscript in a few weeks time.
Yours sincerely,
Rosalind Franklin