directly observed

, were to be accounted for; but they made a most artificial scheme, that still saved the immobility of the Earth. Suppose a person passing around a room holding a lamp, and all the while turning on his heel. 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