16th May, 1955.
Dear Dr. Fraenkel-Conrat,
Thank you very much for the new preparations which I have just received.  I am particularly grateful for the mercury compound.  With these two it should at least be possible to find on what radius the sulfur lies.
It would, however, be desirable to compare them with the TMV from which they were prepared.  I have recently done some work on different strains of TMV and find differences in the X-ray diagram which are appreciable.  I did eventually get a moderately good photograph from the iodine preparation which you sent me before, but the difference between it and other photographs was of the same order as the difference between strains.  So I should be very grateful if you could send me a little of your un-treated TMV for comparison.
Yours sincerely,
Rosalind Franklin.