The weight C will turn around the centre A and will first come to D, thence to E, thence to F and G; then it will return to C, having described a complete circle, C D E F G; then it will again move to D, E, F, etc., and so perpetually, since there is no reason for its stopping in any point of the circle rather than in another. [Illustration] That indeed the weight C affixed to the gnomon will move from C to D, is proved by daily experience, by which it is established that a gnomon so contrived and placed erect on any flat space, will not be able to stand, but the arm B C, C preponderating, will move towards D. It may in the second place be proved, that if, on the other hand, another arm B G be added to the gnomon, equal in weight and similar to the other, the whole G B C A will remain motionless in equilibrium; therefore the arm B G being taken away and equilibrium being destroyed, the arm B C must move in the opposite direction. The above, from Scheiner, called forth the following from Schott, who was also an eminent mathematician: Whether there could be a perpetual artificial motion around the centre of the earth? [Illustration] We have treated this question in our Hydraulico-pneumatic Mechanics, Part 2, Class 2, Machine 13, not however universally, but only in one particular case, that of the Gnomon of Scheiner. For P. Christopher Scheiner, in "Mathematical Disquisitions," in Number XV., Corollary 4, asserts Perpetual Artificial Motion not to be repugnant to Nature, and attempts to prove it in the following manner. Let a gnomon of a certain weight A B C be suspended around A, the centre of the universe, and bound to the beam D F, which is supported by the columns D F and E G and turns at the pole D or E; or let it be fixed at the poles, but the gnomon revolving at A.