January 8, 1931

Professor P. Debye,

Physikalisches Institut der Universitat,

Linnestrasse 5, Leipzig, Germany

Dear Professor Debye:

I have read with much interest your discussion of anomalous dispersion in ice with its accompanying assumption of some freedom of rotation of the molecules. Mr. Cone at Berkeley has recently found a pronounced change in the dielectric constant of solid HCl, from 10 above 98.44°K to 2.5 below that temperature, substantiating the conception that the molecules rotate with considerable freedom in the high-temperature form and are firmly held in the other form.

Mr. Brockway, a student working with me, has been making X-ray diffraction photographs of solutions, and as a consequence both he and I are deeply interested in your work. Could you send me two copies of each of the following papers, if they are available:

Ann.d.Phys., 46, 809 (1915)

Phys.Zeit., 31, 419 (1930); 30, 84 (1929); 28, 135 (1927).

With best wishes, and expressing my regret that I had not before noticed your work on molecular rotation, I am

Very sincerely yours,

LP:M