Baade gives reply to some questions asked by Pauli: 1) About the deviation of light in the gravitational field. 2) About the gravitational red shift. 3) About the Hubble constant.

Bohr thanks Pauli for his congratulations on his 65th birthday. He writes about the double role of a human being as an observer and as an actor in the theatre of life. He also speaks of the preparation of an article on free will and life, and of a book based on his Grifford lecture.

Bohr does not agree with Pauli's and Heisenberg's criticism of Thomas' work in: Nature : 117 (1926), pp. 514. He discusses the problem in detail and asks for further comments from Pauli.

Bohr is on vacation in Arosa with Harald. He hopes to see Pauli when coming through Hamburg on their return and will talk about Pauli's planned visit to Copenhagen. Bohr has sent an entirely new manuscript to Berlin for "Naturwissenschaften : 16 (1928), pp.245".

Bohr will pass through Hamburg together with Klein on their way to Holland. He hopes that Pauli will join him on his way back to Copenhagen.

Bohr has heard that Pauli developed new thoughts on the mystic of relativity in the atom theory and is asking for some developments.

Bohr discusses Goudsmit and Uhlenbeck's work published in: Nature : 117 (1926), pp.264. Thomas has explained the missing factor of 2 by calculating the relativistic motion in: Nature : 117 (1926), pp.514. Thomas' note is enclosed.

Bohr comments on a book by A Pauly (1905) on "Darwinism and Lamarchism". Bohr gives his attitude to the great progress in biology and psychology made in recent time, in the light of the results of atomic physics as regards the description of phenomene.

Ehrenfest is looking forward to see Pauli in Leiden. he mentions some papers by Heisenberg, Hund and on group theory, on which he wants to ask Pauli several questions.

Ehrenfest sends a short note in which he expresses his doubts as to the separability of the operator-function M representing the spin interaction of the two He-electron.