position towards the horizontal, is shut, so that the mercury always retains its proper position in the tubes or cylinders, and is acted on by the pressure of the atmosphere at those points only where such pressure can be of service. The power of this wheel will be, of course, in proportion to the vacua produced in manner aforesaid, and to the altitude of the columns of mercury employed. The inner cylinders might be dispensed with, and the tubes be made to communicate directly with each other, but I prefer, for most purposes, the arrangement which I have before described, with the two intermediate cylinders A¹, B¹; where the inner cylinders are dispensed with, I make use of eccentrics instead of the joined levers before described, to enable the weights to turn to the extent of about half a circle. The number of tubes also need not be limited to four, but increased to any convenient extent. Prof. George Sinclair's Device This device was invented by George Sinclair, who was a professor of philosophy at Glasgow University. He died in 1696. In 1669 he published a work on Pneumatics, and in that work claimed to have discovered Perpetual Motion. Explanations of his device consumed eighteen pages of a Latin work on Pneumatics. It very absurdly depended for its operation upon the delivery of water from the short leg of a siphon, instead of the long leg. The figure illustrates the contemplated operation. [Illustration] Jacob Brazill's Device In 1839 Jacob Brazill, of Deptford, Kent, Governor of Trinity Ground, applied for a British patent on "Improvements in Obtaining Motive Power." In his application he describes his alleged invention as follows: My invention consists in a certain arrangement or combination of mechanism wherein the atmospheric air is employed as the impelling agent, being brought to bear in such a manner as by exerting a constant urging pressure, to produce a continuous rotary motion, and applies to all the purposes where a prime mover is required. [Illustration]