British physicist, chemist, and mathematician (1862-1942) who shared the 1915 Nobel Prize in Physics with his son Lawrence Bragg, for 'their services in the analysis of crystal structure by means of X-rays.' TLS signed “W. H. Bragg,” one page, 5 x 7, University of London letterhead, January 25, 1919. Letter to Dr. Ludwik Silberstein, in full: "I am puzzling over a point which involved the momentum and energy of a high speed electron. I wonder if you would be so good as to give me the benefit of your advice? Could I meet you anywhere on Monday? It would be very nice if you would come and have a cup of tea here about 4 o'clock, or later if it suits you better." Silberstein notes the dates of receipt and reply on the reverse. In fine condition.
From the collection of physicist Ludwik Siberstein.