TZ'S manual, but in the privacy of the atom they indulged in strange and unnatural practices; they oscillated in ways which no well-behaved mechanical system would deem proper. What was to be said of particles which were ignorant apparently of even the rudiments of dynamics? Who could apologize for such perversity rationalize the data of spectroscopy? A genius was called for, and a genius appeared. In 19I 3 N ELS BO tR gave us his strange conception of "stationary" orbits in which electrons rotated end- lessly without radiating, of electrons disappearing from one. orbit and reap- pearing, after brief but unexplained absences, in another. It was a weird picture -- a picture to delight a Surrealist but one which fascinated the