Pauli suggests some physical properties of neutrino and criticizes de Broglie's idea of light quantum as two neutrinos.

Pauli asks for clarification of beta-decay Hamiltonian.

Pauli writes on some afterthoughts about Heisenberg's letter.

Pauli writes that his view that Delta-type interaction between more than two neutrinos must lead to infinities was influenced by a paper by Thomas (Phys. Rev. 47,903). This does not affect Pauli's and Heisenberg's case.

The letter asks further question about the same model discussed in his letter of 14 Nov, concerning impact cross-section of suchparticles.

Pauli takes back what he said in the last postcard and confirms Heisenberg's calculations.

Pauli comments on a paper by Uhlenck-Konopinski and by Anderson-Neddermeyer on particles with masses between that of electron and proton, which opens completely new vistas.

Bloch has given Pauli Bohr's letter and the note on the nuclear photo-effect to read. At Bohr's request, Pauli gives his opinion on it.

Pauli congratulates Heisenberg on the birth of his child. He makes a remark on the cut-off frequency of long waves and about Yukawa's theory of nuclear forces.

Pauli talks more about cosmic rays and the occurence of light particles (electrons) in showers.