19th October, 1973 Dear Paul, I was naturally disappointed not to receive your exciting photos of SV 40 chromatin via the Kornbergs. I understand from Roger that you have said that both the configurations sketched in my letter of 18th September appear in your photos. However I cannot easily see how the description of the doughnut given in your letter to me (undated; received here 5th September) as 100 angstroms thick and "a contour length of 0.1 that of the free circular DNA" can possibly be correct if the DNA has a molecular weight of 3.4 x 10 [to the sixth] and therefore a length, naked, of about 17,000 angstroms. Have you shown that the doughnuts contain the full SV 40 DNA? Or does the written description given in your letter apply to the more extended snake-like forms? We are still hoping to receive some of your pictures (with dimensions marked on them) but if you and Griffith feel that you cannot release them at this stage I would be glad if you would let me know as soon as possible, as in that case we shall have no choice but to repeat the work independently. Best wishes to all at Stanford. Yours sincerely, Francis