Louis Harold Gray was a pioneering radiation biologist, specializing in radiation therapy for cancer. Franklin had consulted
him regarding the tendency of virus samples to break down when exposed to x-rays, one of many challenging aspects of her TMV
research. He suggested several remedies in response. In this follow-up letter, he offered to have her irradiated samples analyzed
to determine exactly how much radiation they had absorbed.
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1957-03-20 (March 20, 1957)
Gray, L. H.
British Empire Cancer Campaign Research Unit in Radiobiology
Original Repository: Churchill Archives Centre. The Papers of Rosalind Franklin
Thank you for your letter of March 14th. I wondered if you might be interested in attempting a direct measurement of the
dose received by your crystal. At dose levels of 5 10 [to the fifth] r irradiated perspex develops absorption bands and if
a suitable wave length is chosen in one of these bands the extinction coefficient is proportional to dose. My colleague Dr.
Boag has collaborated with Professor Rotblat and others at St. Bartholemew's Hospital in developing this method of dosimetry.
If you care to expose any or all of the enclosed specimens of perspex, normally to your X-ray beam, and return them to me,
Dr. Boag will examine their absorption spectrum and may be able to give you some information regarding the dose which they
have received. On the basis of these tests you would know whether you were interested in making further measurements, in
which case Dr. Boag would be pleased to give you full information. The method is being written up but is not yet in print.