  The following is a translation of the paper by Walther Gerlach and Otto Stern
that reported the first evidence for the quantisation of atoms in a magnetic
field. The atoms have quantum states corresponding to a limited number of
possible angles between the directions of the angular momenta of the atoms and
the magnetic field, also called space quantisation. Wording and layout have
been chosen to be as close to the original as possible. For context we
recommend the recent review.
