Attempts to discover a PERPETUAL MOTION are still made in almost every country. In the United States a successful result is attained, according to the newspapers, about twice a year, and in Europe the inventive genius of the people is nearly as well rewarded. We read in the French paper appearing in Constantinople, that a Polish refugee of the name of Rudinski has discovered a sort of _perpetuum mobile_, at least an engine which somewhat approaches perpetual motion, for when once put in motion it can preserve it for twenty years. The power of this engine is said to be greater than that of any other yet known. The article in the same paper says that the inventor has made as a model a small carriage, 22 inches long, 11 inches wide and 14 inches high; that it carries a burden of one ton; and that its speed is a mile in a minute. The inventor is now occupied in building a mill after his method for the Turkish Government. The last American effort in this line is a "Static Pressure Rotary Engine," advertised by a Mr. Sawyer, and vindicated by Mr. Andrews, in a series of letters in the Tribune. Professor Loomis, of the New-York University, has taken the trouble to show that there is no discovery in the case. Mr. Sawyer's machine consist a of a covered cylindrical basin, 26 inches in diameter and two inches deep, to which is attached a vertical tube four inches in diameter and of any required length. A spiral groove runs the whole length of the tube, and this, together with the basin, is supposed to be filled with quicksilver. The whole is to be rapidly revolved about a vertical axis, when the centrifugal force of the mercury in the basin drives the mercury out through a valve on the edge of the basin, and leaves a vacuum behind. The mercury, as it escapes from the basin, falls into a reservoir communicating with the bottom of the spiral groove, through which it is forced by the pressure of the atmosphere with such velocity that the reaction of the sides of the groove causes the tube and the attached basin to revolve with great momentum, evolving new centrifugal force by which the vacuum is perpetuated. Mr. Sawyer supposes that the centrifugal force of the revolving mercury is sufficient to maintain its own revolution unimpaired, and leave a large surplus capable of being applied to any useful purpose. This conclusion is founded upon the computations of Professor Bull. Professor Bull has computed that a wheel 16 inches in diameter, and weighing 531 pounds, revolving 25 times in 10 seconds, will have a centrifugal force of 2,716 pounds; and that this velocity may be produced by a power of 166 pounds applied 1-1/2 inches from the centre, or a power of 452 pounds acting on the spiral groove already mentioned. Hence, says Mr. Sawyer, we have "a clear surplus of 2,264 pounds more than is required to turn the wheel." If this were so, it would constitute the most beautiful perpetual motion ever dreamed of by the visionary. Professor