rapidity of condensation, but enabling the designer to employ a comparatively small receiver or condenser. The engine is shown in Fig. 15, which is copied from the "Experimental Philosophy" of Desaguliers. FIG. 15.-Engine built by The receiver, A, is connected to the boiler, B, by a steam-pipe, C, terminating at the two-way cock, D; the "forcing-pipe," E, has at its foot a check-valve, F, and the valve G is a similar check at the head of the suction-pipe. His a strainer, to prevent the ingress of chips or other bodies carried to the pipe by the current; the cap above the valves is secured by a bridle, or stirrup, and screw, I, and may be readily removed to clear the valves or to renew them; K is the handle of the two-way cock; M is the injection-cock, and is kept open during the working of the engine; L is the chimney-flue; N and O are gauge-cocks fitted to pipes leading to the proper depths within the boiler, the water-line being somewhere between the levels of their lower ends; P is a lever safety-valve, as first used on the "Digester" of Papin; R is the reservoir into which the water is pumped; 7 is the flue, leading spirally about the boiler from the furnace, V, to the chimney; Y is a cock fitted in a pipe through which the rising-main may be filled from the reservoir, should injection-water be needed when that pipe is empty. Seven of these engines were built, the first of which was made for the Czar of Russia. Its boiler had a capacity of "five or six hogsheads," and the receiver, "holding one hogshead," was filled and emptied four times a minute. The water was raised "by suction" 29 feet, and forced by steam pressure 11 feet higher. Another engine built at about this time, to raise water 29 feet "by suction," and to force it 24 feet higher, made 6 "strokes" per minute, and, when forcing water but 6 or 8 feet, made 8 or 9 strokes per minute. Twenty-five years later a workman overloaded the safety-valve of this engine, by placing the weight at the end and then adding "a very heavy plumber's iron." The boiler exploded, killing the attendant. Desagulier says that one of these engines, capable of raising ten tons an hour 38 feet, in 1728 or 1729, cost £80, exclusive of the piping. Blakely, in 1766, patented an improved Savery engine, in which he endeavored to avoid the serious loss due to condensation of the steam by direct contact with the water, by interposing a cushion of oil, which floated upon the water and prevented the contact of the steam with the surface of the water beneath it. He also used air for the same purpose, sometimes in double receivers, one supported on the other. These plans did not, however, prove satisfactory. Rigley, of Manchester, England, soon after erected Savery engines, and applied them to the driving of mills, by pumping water into reservoirs, from whence it returned to the wells or ponds from which it had been raised, turning water-wheels as it descended. Such an arrangement was in operation many years at the works of a Mr. Kiers, St. Pancras, London. It is described in detail, and illustrated, in Nicholson's "Philosophical Journal," vol. i., p. 419. It had a "wagon-boiler" 7 feet long, 5 wide, and 5 deep; the wheel was 18 feet in diameter, and drove the lathes and other machinery of the works. In this engine Blakely's plan of injecting air was adopted. The injection-valve was a clack, which closed automatically when the vacuum was formed. The engine consumed 6 or 7 bushels of good coals, and made 10 strokes per minute, raising 70 cubic feet of water 14 feet, and developing nearly 3 horse-power. Many years after Savery's death, in 1774, Smeaton made the first duty-trials of engines of this kind. He found that an engine having a cylindrical receiver 16 inches in diameter and 22 feet high, discharging the water raised 14 feet above the surface of the water in the well, making 12 strokes, and raising 100 cubic feet per minute, developed 23 horsepower, and consumed 3 hundredweight of coals in four hours. Its duty was, therefore, 5,250,000 pounds raised one foot per bushel of 84 pounds of coals, or 62,500 "footpounds" of work per pound of fuel. An engine of slightly greater size gave a duty about 5 per cent. greater. When Louis XIV. revoked the edict of Nantes, by which Henry IV. had guaranteed protection to the Protestants of France, the terrible persecutions at once commenced drove from the kingdom some of its greatest men. Among these was Denys Papin. It was at about this time that the influence of the atmospheric pressure on the boiling-point began to be observed, Dr. Hooke having found that the boiling-point was a fixed temperature under the ordinary pressure of the atmosphere, and the increase in temperature and pressure of steam when confined having been shown by Papin with his "Digester." DENYS PAPIN was of a family which had attached itself to the Protestant Church; but he was given his education in the school of the Jesuits at Blois, and there acquired his knowledge of mathematics. His medical education was given him at Paris, although he probably received his degree at Orleans. He settled in Paris in 1672, with the intention of practising his profession, and devoted all his spare time, apparently, to the study of physics. Meantime, that distinguished philosopher, Huyghens, the inventor of the clock and of the gunpowder-engine, had been induced by the linen-draper's apprentice, Colbert, now the most trusted adviser of the king, to take up his residence in Paris, and had been made one of the earliest members of the Academy of Science, which was founded at about that time. Papin became an assistant to Huyghens, and aided him in his experiments in mechanics, having been introduced by Madame Colbert, who was also a native of Blois. Here he devised several modifications of the instruments of Guericke, and printed a description of them.' This little book was presented to the Academy, and very favorably noticed. Papin now became well known among contemporary men of science at Paris, and was well received everywhere. Soon after, in the year 1675, as stated by the Journal des Savants, he left Paris and took up his residence in England, where he very soon made the acquaintance of Robert Boyle, the founder, and of the members of the Royal Society. Boyle speaks of Papin as having gone to England in the hope of finding a place in which he could satisfactorily pursue his favorite studies. Boyle himself had already been long engaged in the study of pneumatics, and had been especially interested in the investigations which had been original with Guericke. He admitted young Papin into his laboratory, and the two philosophers worked together at these attractive problems. It was while working with Boyle that Papin invented the double air-pump and the air-gun. Papin and his work had now become so well known, and he had attained so high a position in science, that he was nominated for membership in the Royal Academy, and was elected December 16, 1680. He at once took his place among the most talented and distinguished of the great men of his time. He probably invented his "Digester " while in England, and it was first described in a brochure written in English, under the title, "The New Digester." It was subsequently published in Paris.' This was a vessel, B (Fig. 16), capable of being tightly closed by a screw, D, and a lid, C, in 1 "Nouvelles Expériences du Vuide, avec la description des Machines qui servent à le faire." Paris, 1674. "La manière d'amollir les os et de faire cuire toutes sortes de vi andes," etc. |