I have dwelt upon this subject a little after the manner of a lecturer, because so many of the feats performed in the arena of a circus depend upon the natural law which I have endeavoured to explain, and many of my readers, who have witnessed them, without being able to account for them, may like to know something of the _rationale_. It may be asked, and the question is a very pertinent one, why do not equestrians fall in performing feats of horsemanship in a standing position, in which, as the horse careers round the ring, they lean inward? This phenomenon is due to the counterpoise which, in the case of bodies in a state of rapid motion, the centrifugal force presents to the weight of the body. Centrifugal force, it must be explained, is the tendency which bodies have to fly off in a straight line from motion round a centre; and the power which prevents bodies from flying off, and draws them towards a centre, is called centripetal force. All bodies moving in a circle are constantly acted upon by these opposing forces, as may be seen by attaching one end of a piece of string to a ball, and the other to a stick driven into the ground. If the ball is thrown horizontally, with the string in a state of tension, it will fly round the stick; but, if it becomes disengaged from the string, the centrifugal force, or its tendency to fly off, will cause it to proceed in a straight line from the point at which the separation is effected. Let us now see how these forces operate in the case of the riders in a circus. The equestrian leans inward so much that, if he were to stand still in that position, he would inevitably fall off the horse; but the centrifugal force, which has a tendency to impel him outward from the circle, or in a straight line of motion, sustains him, and he careers onward safely and gracefully. The tendency of the centrifugal force to impel him outward is counteracted by the inward leaning, while it forms an invisible support to the overhanging body. It will be observed also that the horse assumes the same counteracting posture; and a horse quickly turning a corner does the same. Resuming our record of circus performances, we find Pablo Fanque at Astley’s in 1847, with a wonderful trained horse, Plége again appearing on the tight-rope, and Le Fort, ‘the sprite of the pole,’ in a novel and clever gymnastic performance. The political events of which Paris was the scene in the following year caused the managers of Franconi’s Cirque to transfer their company and stud to Drury Lane Theatre, so that London had two circuses open at the same time for the first time since the days of Astley and Hughes.