If he turned round uniformly, there would be no actual interruption of the uniform circular motion both of the carrier and the carried; but the light, as seen by an observer in the interior , would make strange gyrations. Unable to account otherwise for the irregularities of the planets, they mounted them in this manner, on small circles, whose centres only revolved regularly around the Earth, but which, during their revolutionary motion, also revolved around their own centres. Styling these cycles and epicycles, the ancient learned men framed that grand system of the Heavens concerning which Ptolemy composed his ‘Syntax.’ ” ↩