That the earth revolves round the sun, and rotates on its polar axis, have long been the settled canons of our system. But the rotation of the earth has been rendered _visible_ by a practical demonstration, which has drawn much attention in Paris, and is beginning to excite interest in this country. The inventor is M. Foucault; and the following description has been given of the mode of proof: "At the centre of the dome of the Panthéon a fine wire is attached, from which a sphere of metal, four or five inches in diameter, is suspended so as to hang near the floor of the building. This apparatus is put in vibration after the manner of a pendulum. Under and concentrical with it, is placed a circular table, some twenty feet in diameter, the circumference of which is divided into degrees, minutes, &c., and the divisions numbered. Now, supposing the earth to have the diurnal motion imputed to it, and which explains the phenomena of day and night, the plane in which this pendulum vibrates will not be affected by this motion, but the table over which the pendulum is suspended will continually change its position in virtue of the diurnal motion, so as to make a complete revolution round its centre. Since, then, the table thus revolves, and the pendulum which vibrates over it does not revolve, the consequence is, that a line traced upon the table by a point projecting from the bottom of the ball will change its direction relatively to the table from minute to minute and from hour to hour, so that if such point were a pencil, and that paper were spread upon the table, the course formed by this pencil would form a system of lines radiating from the centre of the table. The practiced eye of a correct observer, especially if aided by a proper optical instrument, may actually see the motion which the table has in common with the earth under the pendulum between two successive vibrations. It is, in fact, apparent that the ball, or rather the point attached to the bottom of the ball, does not return precisely to the same point of the circumference of the table after two successive vibrations. Thus is rendered visible the motion which the table has in common with the earth."