These three letters are about progress in Pauli's work on the He-model and some technical questions concerning his coming to Copenhagen.

Heisenberg writes on excitation times and line widths.

Pauli talks about a model for the explanation of the Zeeman-effect.

Pauli talks about his decision to go to Hamburg. He writes about the difficulties of Bohr's theory of the periodic system. He makes observations about equivalent electron orbits. He says that there is a failure in classical mechanics. He comments on the introduction of half-integer values for j and m. He talks about his own work on the anomalious Zeeman-effect and about Heisenberg's theory of doublets.

Pauli thanks Landé for his communication about the summation rule.

Pauli complains to Bohr for taking Kramers with him to England at a time when himself is so much in need of Kramers' company.

Pauli thanks Eddington for his book on relativity he has sent to him. He explains the reasons for his opinion that Eddington's attempt of a formal unification of electromagnetic and gravitational field have no physical significance.