Pauli writes about the paper by Bohr, Kramers, Slater and its experimental refutation by Geiger and Bothe. Pauli explains that the concepts of motion and force have to be modified, but not the concept of energy. He writes of his support for Heisenberg's new ideas.

Pauli talks about his work with Heisenberg on field theory. He makes remarks on Dirac's electron theory.

Pauli says that Goudsmit told him about Thomas' calculations, and this confirms his ideas about the definition of the moment of the electron. Pauli gives some consideration to the implications of the model of the rotating

Pauli discusses the properties of spin matrices and efforts toward a quantum electrodynamics.

Pauli writes about mathematical contributions to the quantum-mechanical calculus.

Pauli discusses the question of a degenerated gas and compares statistics of Bose-Einstein with that of Fermi-Dirac. Another part of the letter deals with scattering which Pauli does not yet understand.

Pauli hopes to come to Copenhagen and to discuss radiation problems. He has now to write a Handbuch article for Springer on the problem of closed shells. He believes in a definite value of momentum of the atom in a stationary state, if this momentum is conceived as a dynamical (not kinematical) quantity. He writes also about the theory of multiplet intensities in an electric field, Ornstein's sum-rules, Kramer's dispersion theory and about the so-called Smekal-jumps (frequency of the external field goes to zero).

Pauli thanks Einstein for the proofs of his paper (written by Einstein with Ehrenfest) concerning the elementary processes in which several quanta are simultaneously absorbed or emitted. Pauli shows that there exists an analogue for such processes in classical theory.

The letter talks about Pauli's visit to Copenhagen in April and about the progress he made in the kinetic of heat conduction in solids.

Bohr thanks Bohr for his letter of the 25th September.