Suppose the fire burning, and the boiler sending forth steam, and the key of cock k turned so as to permit the steam to enter into the vessel a b e d, then will the steam drive out all the air of that vessel up the force pipe x x x x, and occupy its place; steam will then be seen to issue from the nosle w of the force pipe. When this is observed, the key of the steam cock k must he turned, to permit the steam to pass into the vessel e f g h, and at the same time the key of the cold water cock n must also be turned, to permit the water from the fountain to be forced into the vessel a b e d, (by the pressure of the atmosphere) as the steam therein condenses with the cold water; and when the vessel abed is filled with water, and the vessel cf h with steam, the key of the steam cock k is to be turned back into its lirst position, which will again permit the steam to pass into the vessel a b c d, to act upon the surface of the water in that ves sel, so as to drive it up the force pipe x x x, and, at the same time, the key of the cold water cock n must also be turned, to permit the cold water to condense the steam and fill the vessel c f g h, and which will also be forced into this vessel (by the pressure of the atmosphere) to occupy the vacuum effected by the condensed steam. The cock n is next to be turned so as to permit the vessel abed" to force and refill with cold water," and, at the same time, the steam cock k is to he turned, so as to permit the steam to act upon the surface of the water in the vessel e f g h, and so on alternately, producing a constant stream from the top of the force pipe. The boiler may be supplied with water lion, the cistern lAS, by means of a small pipe and stop-cock.
To produce" a constant stream forty feet high, one vessel of water rarefied by tire, driveth up forty of cold water, (or in other words, forty times the quan tity in the boiler.) A man that tends the work is but to turn two cocks, that one vessel of water being con sumed, another begins to force and refill with cold water, (by the pressure of the atmosphere) and so successively, the fire being tended and kept constant, which the self same person may likewise abundantly perform in the interim between the necessity of turn ing the said cocks." Although the Marquis of Worcester has only pro posed to force water by his engine to a great height, yet it appears that he knew that water could have been brought up from a limited depth by suction, (by the pressure of the atmosphere into a vacuum;) for the 68th article commences with these words: "An admirable and most forcible way to drive up water by fire, not by drawing nor sucking it upwards, for that must he, as the philosopher calleth it, intra splarrant activitatis, (within its sphere of activity) which is but at such a distance." It is therefore very obvious, that the Marquis had a knowledge to what height water could have been raised from the effects of a vacuum, and which he had put a small value upon in comparison of what he had in view; for he adds, "but this way bath no bounder if the vessels be strong enough." The Mar quis a little further on says, •‘ so that having a way to make my vessels, so that they are strengthened by the force within them." This can only apply to strengthening his boiler and vessels by rivetting radiating arms inside of them, and making them in other respects strong.
Sir Samuel Morland, celebrated as the inventor of the speaking trumpet, appears to have directed his attention, in 1682, to the force of steam as a means of raising water. In 1681, he was sent by Charles IL to Louis XIV., to direct the execution of water works in France, and while he was in that country in 1683, lie wrote a small treatise in French, entitled Elevation Iles Eattx par Joules sorles des Machines reduite a la Illesure cut Poids, el a la Balance. This work was
presented to the French king. and is preserved in the Ilarleian collection at the British Museum. The chapter on Steam Engines, which occupies only the last four pages, is as follows: "The Principles of the New Force of Fire invented by the Chevalier Illorland in the year 1682, and presented to his Christian Majesty 1683. Water being evaporated by the force of fire, these vapours immediately occupy a much greater space (about 2000 times) than the water occupied be fore, and its power is so great that if closely impri soned it will burst a piece of cannon. But being go verned according to the rules of statics, and reduced by science to measure, weight, and balance, it then bears itself quietly under the harness (like good horses) and becomes of great use to mankind, par ticularly to raise water according to the following table, which shows the number of pounds which can be raised 1800 times per hour to the height of six inches, in cylinders half filled with water, as well as the different diameters and depths of the cylinders.
Among the eminent men who speculated respecting; the use of steam as a moving power, Dr. Denys Papin deserves an honourable place. Driven from his own country by the revocation of the edict of Nantes, he resided in London from 1680 to 1687. He seems to have invented his digester in 1680, and during the ex periments which he made with it, he was necessarily led to observe the expansive force of steam, and to ascertain its great power froin the strength which his digesters required, and the means which were neces sary to keep down their covers. In the .leta Brad/fo rum of Leipsic, for 1690, he has described the follow ing engine, n hich cannot fail to be considered by every candid inquirer as a real step to the invention of the steam engine. A cylinder AA, Plate D1V. Fig. 7. made of thin metal, is fitted with a piston B, which can slide freely up and down in the cylinder. A small quantity of water being put into the bottom of the cylinder, and the piston B depressed so as to touch the water, the air being driven out through a hole in the piston, which is afterwards closed by a plug M. The water being made to boil by a fire be neath the cylinder, it is changed into vapour, which exerts so strong a pressure against the piston that it surmounts the pressure of the atmosphere, and push es the piston upwards to the top of the cylinder. The piston is prevented from descending by a latch E fall ing into a notch in the stem PI of the piston. The lire must now be removed from beneath the cylinder, and the vapours in this cylinder soon recondense them selves into water by cold, and leave the cylinder en tirely free or air. In this state the machine is ready to exert its force, for, by loosening the latch E, the pis ton will be pressed down into the cylinder by the weight of the atmosphere which presses upon its up per surface while there is no air beneath to resist its descent, and a rope fastened to the stem of the piston H may be taken over pulleys TT, and applied to raise weights. Papin actually tried this experiment with a cylinder 21 inches in diameter, by which he raised GO lbs., and he made it repeat its action once in a mi nute. Hence he computed that a cylinder about two feet in diameter and four feet high would raise 8000 lbs. every minute four feet high, which is nearly a horse power.