A file marked "Acta paper on helix" containing a draft typescript for Cochran and Crick, "Evidence for the occurrence of the Pauling-Corey alpha-helix in synthetic polypeptides," Nature, 169 (1952), 234-5.
Also included are related notes and calculations (holograph), graphical data on tracing paper, and two letters to Cochran and Crick from V Vand.
In the letter of 13 December, 1951, Vand writes: "I think that a graphical method might be quite adequate, the evaluation being done by superimposing over the Cn graph a sheet of tracing paper with a properly oriented square net drawn on to it, the scale of the net depending on r and its orientation on the z co-ordinate of the atom. In this way the values of Cn are evaluated on points of a standard square net in reciprocal space, and contributions from different atoms are thus rapidly added at each point of the net. The Sn values can be obtained from the Cn graphs by providing a separate angular scale, say in red. I am sending you a part of my Co graph, in case you have not already plotted one; the evaluation is, as you will see, very rapid."