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April 10, 2026

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April 10, 2026

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"The following is a description of the engine, as far as it was improved by Newcomen. B represents the boiler with its furnace for producing steam, and at a small height above the boiler is a steam cylinder, C, of metal, bored to a regular diameter, and closed at the bottom; the top remaining open. A communication is formed, between the boiler and the bottom of the cylinder, by means of a short steam pipe S. The lower aperture of this pipe is shut by the plate p, which is ground flat, so as to apply very accurately to the whole circumference of the orifice. This plate is called the regulator or steam cock, and it turns horizontally on an axis a, which passes through the top of the boiler, and is fitted steam-tight; and has a handle.. to open and shut it.frameless|right|upright=2.0|Newcomen Engine, Fig. 4 Thomas Tredgold's "The Steam Engine... Invention & Progressive Improvement" A piston P is fitted to the cylinder, and rendered air-tight by a packing round its edge of soft rope, well filled with tallow, to reduce the friction, and its upper surface is kept covered with water to render it steam-tight. The piston is connected to a rod PA, which is suspended by a chain from the upper extremity D of the arched head of the lever, or working beam, which turns on the gudgeon G. This beam has a similar arched head EF, at its other end, for the pump rod H, which receives the water from the mine. The end of the beam to which the pump rod is attached, is made to exceed the weight and friction of the piston in the steam cylinder; and when the water is drawn from such a depth, that the pump piston is too heavy for this purpose, counterpoise weights must be added at I, till the piston will rise in the steam cylinder at the proper speed. At some height above the top of the cylinder is a cistern L, called the injection cistern, supplied with water from the forcing pump [through pipe] R. From this [cistern] descends the injection pipe M, which enters the cylinder through its bottom, and terminates in one or more small holes at N. This pipe has at O a cock, called the injection cock, fitted with a handle. At the opposite side of the cylinder, a little above its bottom, there is a lateral pipe, turning upwards at the extremity, and provided with a valve at V, called the snifting valve, which has a little dish round it to hold water for keeping it air-tight. There proceeds also from the bottom of the cylinder a pipe Q, of which the lower end is turned upwards, and is covered with a valve v; this part is immersed in a cistern of water called the hot well, and the pipe itself is called the eduction pipe. To regulate the strength of the steam in the boiler it is furnished with a safety valve [ sV ]...but not loaded with more than one or two pounds on the square inch. The mode of operation... Let the piston be pulled down to the bottom of the steam cylinder, and shut the regulator or steam valve p. ...Apply the fire to the boiler till the steam escapes from the safety valve, and then on opening the steam regulator, the piston will rise by the joint effect of the strength of the steam, and action of the excess of weight on the other end of the beam. When it arrives at the top of the cylinder, close the regulator p, and by turning the injection cock O, admit a jet of cold water, which condenses the steam in the cylinder, forming a partial vacuum, and the piston descends by the pressure of the atmosphere, raising water by the pump rod H from the mine. The air which the steam and the injection water contain is impelled out of the snifting valve V, by the force of descent, and the injection water flows out at the eduction pipe Q; and by repetition of the operations, of alternately admitting steam and injecting water, the work of raising water is effected."

- Thomas Tredgold

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"My first essay at making a steam engine was when I was fifteen. I then made a real working; steam-engine, 1 3/4 diameter cylinder, and 8 in. stroke, which not only could act, but really did some useful work; for I made it grind the oil colours which my father required for his painting. Steam engine models, now so common, were exceedingly scarce in those days, and very difficult to be had; and as the demand for them arose, I found it both delightful and profitable to make them; as well as sectional models of steam engines, which I introduced for the purpose of exhibiting the movements of all the parts, both exterior and interior. With the results of the sale of such models I was enabled to pay the price of tickets of admission to the lectures on natural philosophy and chemistry delivered in the University of Edinburgh. About the same time (1826) I was so happy as to be employed by Professor Leslie in making models and portions of apparatus required by him for his lectures and philosophical investigations, and I had also the inestimable good fortune to secure his friendship. His admirably clear manner of communicating a knowledge of the fundamental principles of mechanical science rendered my intercourse with him of the utmost importance to myself. A hearty, cheerful, earnest desire to toil in his service, caused him to take pleasure in instructing me by occasional explanations of what might otherwise have remained obscure."

- James Nasmyth

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"AA is a tube of uniform diameter throughout, close shut at the bottom; BB is a piston fitted to the tube; DD a handle fixed to the piston; EE an iron rod moveable round an axis in F; G a spring, pressing the cross rod EE, so that the said rod must be forced into the groove H as soon as the piston with the handle has arrived at such a height as that the said groove H appears above the lid II; L is a little hole in the piston, through which the air can escape from the bottom of the tube AA, when first the piston is forced into it. The use of this instrument is as follows: A small quantity of water is poured into the tube AA; to the depth of 3 or 4 lines; then the piston is inserted, and forced down to the bottom, till a portion of the water previously poured in comes through the hole L; then the said hole is closed by the rod MM. Next the lid II, pierced with the apertures requisite for that purpose, is put on, and a moderate fire being applied, the tube AA soon grows warm, (being made of thin metal), and the water within it, being turned into steam, exerts a pressure so powerful as to overcome the weight of the atmosphere and force up the piston BB, till the groove H of the handle DD appears above the lid II, and the rod EE is forced, with some noise, into the said groove by the spring G. Then forthwith the fire is to be removed, and the steam in the thin metal tube is soon resolved into water, and leaves the tube entirely void of air. Next, the rod EE being turned round so far as to come out of the groove H, and allow the handle DD to descend, the piston BB is forthwith pressed down by the whole weight of the atmosphere, and causes the intended movement, which is of an energy great in proportion to the size of the tube. Nor is it to be doubted that the whole weight of the atmosphere exerts its force in tubes so constructed; for I have established by experiment, that a piston, raised to the top of the tube by the force of heat, shortly afterwards descends again to the bottom, and so on alternately for a number of times, so that no suspicion can arise of air pressing beneath. Now my tube, the diameter of which does not exceed 2 ½ inches, yet raises sixty lbs. aloft with the same velocity as the piston is forced down into the tube, and the tube itself scarcely weighs five ounces. I therefore have little doubt but that tubes may be manufactured, the weight of each of which would scarcely amount to 40 lbs., and yet which could raise, at each operation, two thousand lbs. to a height of four feet. ...If any one now will consider the magnitude of the forces to be obtained in this way, and the trifling expense at which a sufficient quantity of fuel can be procured, he will certainly admit that this my method is far preferable to the use of gunpowder above spoken of, especially as in this way a perfect vacuum is obtained, and so the inconveniences above recounted are avoided."

- Denis Papin

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