Figure 1 of the accompanying drawings represents in horizontal section a square case or cistern; this cistern is filled with water nearly to the top, and two wheels marked _a_, _a_, and _b_, _b_, are placed in the water in the cistern. By capillary attraction the water rises between the two wheels marked _x_, _x_, to a height above the level of the water in proportion to the distance of the wheels from each other at _x_, _x_. As the water rises between the wheels marked _x_, _x_, above its level, the weight of water between the wheels at _x_, _x_, will cause the wheels to continually revolve. Figure 2 represents the same as Figure 1, but in a vertical section. The said power may be obtained by wheels moved on axis, or by other apparatus by rise and fall in the water by vertical motion. The Jurin Device The device which we have designated "The Jurin Device," was not, in fact, invented by Jurin. James Jurin furnished an account of the invention to The Royal Society of London, and it appears in the reports of that society published in 1720. The invention was by a friend of Jurin's whose name he does not give in the account. Jurin's account of his friend's invention is as follows: Some days ago a method was proposed to me by an ingenious friend for making a perpetual motion, which seemed so plausible, and indeed so easily demonstrable from an observation of the late Mr. Hawksbee, said to be grounded upon experiment, that though I am far from having any opinion of attempts of this nature, yet, I confess, I could not see why it should not succeed. Upon trial indeed I found myself disappointed. But as searches after things impossible in themselves are frequently observed to produce other discoveries, unexpected by the Inventor; so this Proposal has given occasion not only to rectify some mistakes into which we had been led, by that ingenious and useful member of the Royal Society above named, but likewise to detect the real principle, by which water is raised and suspended in capillary tubes, above the level. My friend's proposal was as follows: Fig. 1. Let A B C be a capillary siphon, composed of two legs A B, B C, unequal both in length and diameter; whose longer and narrower leg A B having its orifice A immersed in water, the water will rise above the level, till it fills the whole tube A B, and will then continue suspended. If the wider and shorter leg B C, be in like manner immersed, the water will only rise to same height as F C, less than the entire height of the tube B C. This siphon being filled with water and the orifice A sunk below the surface of the water D E, my friend reasons thus: