24 JAN 1956

Peterhouse

Dear Mamma,

Thank you for your letter. I had begun to worry that you were not speaking to me anymore. I shall so it to Linda, who is, I think, returning to Cambridge within the week.

The joker in the local store says there is a three month delay in the arrival or delivery of QUAD amplifiers, and that consequently it should be ordered soon. He also suggests a British made RCA amplifier as being better and with sooner delivery. I do not know whether it is better or not, it does not look as nice.

I have some plans for a super duper gramophone, which I wish to make when I return. The man I want to work with will be in Cambridge. Perhaps I shall stay here for another year. I do not know that Stanley would agree to that, and there is a shortage of electron microscopes here. Perhaps I shall have to come back.

I think the Gray arm is probably not as good as ours, though I am not sure.

Linda’s boy is quite virginal. The Ph.D. ceremony takes three minutes, and I must do some work first. It will be good to see you though. I would like to go on a trip to the south in the summer. Perhaps we could all go to Majorca and work on the Nature of The Chemical Bond for a while. I understand it is quite pleasant for authors there, and I know a chap who works there as a chef or a tourist boat driver or something. He is not very interesting, and neither is Robert Graves, but they would do for a while.

Much love

Peter

24 January, 1956

Dear Daddy,

Thank you for your letter of the 18th. I am glad you are interested in the attack on crystalline globular proteins, as I think that probably the problem can be solved with a lot of work.

We have a micro-densitometer that uses a split light beam and uses the error difference between one beam through the photograph and the other beam through an optical wedge to drive the wedge up and down. There is a pen attached to the wedge. There are two mechanically connected stages, one with the film and the other with a sheet of recording paper, and a screw to drive them. It is quite good, and we use it exclusively. It traverses a straight line, however, and is therefore of greatest use with precession camera photographs, which have an undistorted mapping of the reciprocal lattice. We shall attempt to get as much three dimensional data as possible with precession photographs, though I do not know that we shall be entirely successful. It is not accurate to 2%, the film itself varies more than that, and we measure only peak height and make no attempt to integrate, and while this is reasonable over similar crystals similarly oriented, it will not be as satisfactory on upper layers. The machine was designed by Peter Walker at King’s College, London, and is manufactured more or less by Joyce, Loeble and Company in Newcastle. It costs about 2800 dollars, and needs being worked over after arrival. [Handwritten note: "If you are interested, perhaps we should enquire for you.” and “J L and Co. Ltd. Uline Lane Newcastle-upon-Tyne 1”]

I am of the impression that it is simpler to measure three dimensional spectra with a proportional counter, using converging beam, stationary crystal methods.

I am glad that you have talked to Stanley. I am a little worried about the fellowship, and a little worried that Robley Williams will be here. I must write him.

I should be glad to see you in the summer. If something does not appear in my difference Pattersons, I shall be a little stuck. I was very hopeful from one projection and the one dimensional Pattersons, but the second projection is not pretty. Howard Dintzis has a new heavy metal, however, and is making me some crystals. I am working on the orthorhombic form of Sperm Whale myoglobin, which I think is more suitable for three dimensional work than the monoclinic form.

While I think you would do well to have some densitometers around, the more I think about trying to get three-dimensional data on film, the more I feel a counter spectrometer is better. I understand that a two circle gadget to fit on the GE Powder spectrometer to the design of the Harker one is being made by Supper or someone. Holmes would be against buying such a thing and I think I would agree with him. However, perhaps his great big spectrometer would be suitable. The King’s people (Peter Walker) are working on flying spot integrating photometer, which will probably work and would be excellent for Weissenberg photographs and other distorted spot shape photographs.

Much love

Peter