Pauli repays a loan.

Pauli writes about intercombination lines, and perturbations between singulet and triplet lines in Hg. He speaks about the formulas for the relative intensities of multipletlines and the problem of resonance radiation.

Pauli talks about spectral terms for oxygen. He finds support for Landé-Heisenberg "branching rule" and "Heisenberg's theory". He comments Kronig's formulas. He makes personal remarks on Lenz.

Pauli sends Bohr a short summary of his calculations on the H-atom using the "Göttinger" quantum mechanics. He writes about the difficulty of the excluded pendulum orbits (R=0), about the great progress made by Heisenberg on quantum mechanics and on Heisenberg's theory which may actually not not suffice to explain the two-term system of He. He also talks about other problems that are still open, like the time-dependent processes.

Pauli discusses and criticizes the Sommerfeld and Unsöld's paper on spectroscopy and their electron-spin idea for hydrogen fine structure.

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 admits that his objections against Thomas' Theory of fine-structure are not valid, (i.e. that thte concept of spin has to be accepted).

Pauli writes about his calculations of the Balmerline intensities with the help of Schrödinger's calculus.

Pauli is glad about the changes Bohr made in his manuscript, in particular about his explanation of complementarity. He looks forward to meeting him in Hamburg.

Pauli hopes that Kronig will accept the post of Pauli's assistant in Zürich.