Louis Harold Gray was a physicist and radiation biologist who specialized in the application of radiation to cancer therapy.
Franklin had sought his advice regarding the tendency of viruses to break down during long exposures to x-rays, one of the
many challenges in her virus work. In this letter, she accepted his offer to have one of her x-ray exposures analyzed for
the exact dose level.
Number of Image Pages:
1 (42,657 Bytes)
1957-03-25 (March 25, 1957)
Gray, L. H.
Mount Vernon Hospital
Original Repository: Churchill Archives Centre. The Papers of Rosalind Franklin
Reproduced from the Franklin Collection at the Churchill Archives Centre with the permission of the copyright holder.
We have exposed one of the pieces is of perspex which you sent me, and I am now returning it to you. The X-ray exposure was
overall a length of 15 mm in the centre of the piece, and lasted 20 hours. Because no collimator was used, the intensity
would be slightly greater than that which reaches of virus crystal, but the total exposure would be about the same as one
of the longest exposures of a crystal. I should be very interested to know what does level this corresponds to. I gather
from a recent discussion with Dr. Perutz that 5 times 10 [to the fifth] may be an under-estimate.