The description of the perpetual pump has suggested to me whether the long-sought "perpetual motion" may not be found by a simple mechanical alteration of that machine, and substituting a cannon-ball as a _primum mobile_, in lieu of the water, not always obtainable. I would recommend that in the bottom of the trough be inserted at each end two dropping-boards, of a triangular form, moving on an axis at one corner, one of which falling below the level of the trough at the elevated end, the other shall be raised by the stop affixed to the standard-post, which, throwing the ball again back to the former end, shall depress that, until the same process is repeated in perpetual activity. DESCRIPTION.--Fig. 1. A, the trough, swinging on an axis at B. C, the cannon-ball, raised by one of the dropping-boards, D, whilst the other falls through the opening at E, into the trough. F, the support or stop, raising the dropping-board D. The center of the trough ought to be pierced, leaving the sides as a support to the ball, which ought not to be wider than the ball may travel freely through. [Illustration] Fig. 2. D D, the dropping-boards, which pass through the center so as to leave a sufficiency of the trough as a resting place for the ball to give a momentum, and depress the trough, previously to its being again raised by the dropping-board. We meekly venture to call the attention of this inventor, if he is still living, and to any others who may be working along the same line, that to our certain knowledge water is more generally obtainable than cannon-balls. We, therefore, suggest the use of water instead of cannon-balls. Unpublished Incline Plane and Weights Devices Noted by the Author Except the preceding three devices the author does not remember ever to have seen reported in any book, patent, application for patent, or report, the account of a device for obtaining self-motive power by means of weights and inclined planes, and yet, it is believed by the author from the use that has been made of inclined planes and rolling weights in demonstrating mechanical principles by many natural philosophers, and also from devices that have from time to time been brought to the attention of the author during thirty years last past, that the inclined plane with rolling weights has been a fertile field of folly among Perpetual Motion seekers. On a number of occasions the author has been asked to view and inspect mechanical devices of that kind, which it was claimed by the confident inventor and his friends "would surely work when just one little thing could be overcome." The phraseology was sometimes varied a little from the preceding quotation, but the substance was always there.