The annexed figure exhibits a second form of the machine. A and B are two horse-shoe magnets, _a_ and _b_ the _mysterious substance_, and _m n_ the needle, which turns constantly with great rapidity. Mr. Playfair and Capt. Kater have inspected both of these machines, and are satisfied that they resolve the problem of _perpetual motion_. Joannis Theisneri's Semi-Circle An account of this invention has been preserved by Gaspar Schott in a work entitled "Thaumaturgus Physicus, sive Magiae Universalis Naturae et Artis," published in 1859. It is illustrated by the following figure: [Illustration] The inventor expected the operation of his device to be as follows: "A" is a large magnet, elevated on a short pillar at the foot of which is a straight inclined tube, "C" "F" the ends of which are connected with a curved or semicircular tube "C", "D", "E", "F", as shown in the figure. The weight at the lower extremity is supposed to ascend through the curved tube by the attraction of the magnet "A" and upon reaching the point "C" the supposition was that upon passing the point "C" the attraction of the magnet "A" would be sufficient to hold it there * * * back to the point "F" through the straight tube, and then be drawn by the magnet through the curved tube to the point "C" and so on perpetually. The impracticability of the above device is manifest. At a point between "D" and "E" it is plain the ball would have to ascend perpendicularly and if the magnet exerts sufficient attraction to elevate the weight at that point it would surely hold the weight at the point "C", for at "C" the weight would be much nearer the magnet and consequently much more strongly attracted. Device of Dr. Jacobus In the same work by Gaspar Schott from which an account of the preceding device is obtained he gives an account of the device of Dr. Jacobus. Dr. Jacobus's scheme is illustrated by the following figure: [Illustration] It will be observed that the above figure shows a string of iron balls "A" suspended on a grooved wheel "E" on an axle "C" between two uprights "FF". At "H" lies a large lodestone, which is to attract the balls at "D" and was expected by the inventor to cause the wheel to rotate. CHAPTER VI DEVICES UTILIZING CAPILLARY ATTRACTION AND PHYSICAL AFFINITY Ludeke and Wilckens's Device In 1864, Johann Ernst Friedrich Ludeke, of London, and Daniel Wilckens, of Surrey, applied for British patent on "Improvements in Motive Power by Capillary Attraction." They describe their invention as follows: Our invention consists of improvements in motive power by capillary attraction constructed as follows: [Illustration]