Physicist; he was the first to isolate the electron and measure its charge. TLS, one page, 8.5 x 11, California Institute of Technology letterhead, February 6, 1931. Millikan takes a man to task on a theory. In part, “That from a standpoint of an experimentalist like myself, and also from that of a theorist like Professor Einstein, the one check on equations which enable us to predict new results lies in the agreement or disagreement of the predicted and observed phenomena.” In fine condition, with rusty paperclip marks to left edge and expected folds. R&R COA.