Named in honor of James R. Arnold, professor of chemistry at the University of California at San Diego, distinguished for his applications of nuclear chemistry to the interpretation of meteorites, the history of cosmic radiation, the lunar regolith and compositional mapping of the Moon. In order to elucidate the origin of meteorites he developed a Monte Carlo method for studying the effects of close planetary encounters on the orbital evolution of small planet-crossing bodies. The method has become the primary technique for investigating the dynamical history of planet-crossing asteroids, of which (2143) is an example. (M 4788) _ _.