The rings of Saturn and Uranus

Nature has presented us with two systems of planetary rings. They are not at all similar. Saturn has bright, broad rings separated by narrow gaps. The rings of Uranus are dark, narrow and widely spaced. Presumably both sets of rings lie inside the Roche limit and this is why the ring material has not condensed into satellites. The author briefly reviews what is known about each ring system with particular emphasis on properties of significance to dynamical astronomy. (Auth.)