August 12, 1938

Dr. Ralph W. G. Wyckoff

Laderle Laboratories

Pearl River

New York

Dear Wyckoff:

Dr. David Harker has a very good understanding of crystal structure methods, of quantum mechanics in its chemical applications, and of modern structural chemistry in general. He is, I believe, thoroughly equipped to give advanced courses in these subjects and to direct research as well as to teach elementary chemistry as ho is doing at Johns Hopkins.

As a graduate student here he carried out several interesting structure determinations — pyrargyrite, tetradymite, CuCl₂, 2H₂O. He also developed an interesting and useful variant of Patterson's Fourier series method, and discovered the Murdock circles independently of Murdock. He made an excellent record in my course in the quantum mechanics, and carried out an original investigation of some orthogonal functions. This work was not published because the functions were discovered later to have been already treated by a mathematician.

Harker is a very pleasant man personally. He was trained in a somewhat unconventional manner at a progressive elementary and preparatory school and when he came hero to do graduate work he was erratic and unreliable. He improved in regard to industry and responsibility very much during his years here, and I think that he may well be thoroughly responsible now. I understand that people at Johns Hopkins are well pleased with the way in which he has been teaching freshman

Chemistry. He has not carried on much research there, probably because his teaching has taken up most of his time.

So far as personality, intelligence and ability are concerned, I think that Harker is one of the best men we have had.

Sincerely yours,

Linus Pauling

LP/bcs