Refraction, a bending of light by passing through any medium, as air, water, prism.
Retrograde motion, the apparent movement of a planet from east to west among the stars.
Revolution, the movement of bodies about their centre of gravity.
Rotation, the motion of a body around its axis.
Satellites, smaller bodies revolving around planets and stars.
Saturn, elements of, [167]; revolution of, [168]; rings of, [169]; decreasing, [171]; nature of, [171]; satellites of, [172].
Seasons, of the earth, [102]; of other planets, [105].
Selenography (lunography), a description of the moon's surface.
Signs of the zodiac, the twelve equal parts, of 30° each, into which the zodiac is divided.