156 WOLVERHAMPTON ENGINE. this, added to the imperfect vacuum, that could only be formed by the cooling of the outside of the cylinder, made Newcomen's, in the comparison, a much less effective machine than Savery's, and quite as expensive. The opening and shutting of the cocks by hand practised in both, made them equally inconvenient in this respect, but still the advantage lay with Savery; for inattention on the part of the attendants was not productive of so much irregularity as with the lever engine -this last requiring a degree of precision, much greater than was demanded by the other. Desaguliers relates that, in 1711, an offer made by Newcomen, to drain water from a mine at Griff, in Warwickshire, was not accepted, from a doubt as to its practicability; but that in the succeeding spring, Newcomen succeeded, through his friend, Mr. Potter, of Bromsgrove, in Worcestershire, in getting a contract to draw water from a mine belonging to a Mr. Back, at Wolverhampton*. The account of their first trial is curious, as exhibiting the difficulties the inventors had to cope with, even after the machine was invented ; although carried into execution in a rough way, it was still far from being in a state able to realize even moderate expectations. "After a great many laborious attempts, having at last made the engine work, but not being philosophers enough to understand the reasons, or mathematicians enough to calculate the powers and proportions of the parts, they very luckily found by accident what they sought for.-They were at a loss for the pumps, but being so near Birmingham, and having the assistance of so many admirable and ingenious workmen, they soon came to the method of * P. 533. vol. ii. Experimental Philosophy. INVENTION OF INJECTION. 157 making the pump, valves, clacks, and buckets, whereas they had but an imperfect notion of them before*." The erection of this machine led to an improvement which added prodigiously to its power, as well as to the uniformity of its operation. The usual manner of condensing the steam by cooling the cylinder was not so effective in practice, as at first sight it might appear to be, the vacuum produced by this means was exceedingly imperfect; a defect in their apparatus, the existence of which was cautiously guarded against, as being a great aggravation of this defect, led not only to its entire removal, but to the simplification in no ordinary degree of the general mechanism of the engine. It was of essential importance to the action of the piston, to keep the cylinder beneath it free from air, and to guard in the most effectual manner against any gaining admission by the sides of the piston: for this purpose, a quantity of water was kept laying upon it, which was from time to time renewed from the cistern by a cock and pipet. On the first trials of this engine, the inventors were surprised to see it “ go several strokes, and very quick together; when, after a search, they found a hole in the piston, which let the cold water in to condense the steam in the inside of the cylinder, whereas before they had always done it on the outside." This fortunate discovery led to the mode of condensing the steam by an injection of cold waste inside of the cylinder, instead of doing the same thing by cooling the surface of the outer vessel; and this also suggested a method of regu * P. 533. vol. ii. Experimental Philosophy. P 158 CAMBDEN HOUSE. lating the speed of the apparatus, when the weight on the pumps was variable, or the engine working against a resistance beneath its power: a larger or a smaller quantity of injection water thrown into the cylinder, produced a less or a more perfect vacuum. In the figure (marked NEWCOMEN, B.), the parts remain as before, but instead of the water flowing into the concentric space, the vessel which formed it was dispensed with, and a pipe, n, and cock, p, (called the injection pipe and injection cock,) proceeding from the cistern, was inserted into the bottom of the cylinder. When that vessel was filled with steam, turning the injection cock, p, allowed a jet of cold water to rise through the vapour: by this means the condensation, when compared with the other process, was complete and instantaneous. The greater quantity of water which had now to be removed from the cylinder was taken of by the syphon pipe,i, as before; and the air which was introduced by the same means, also escaped from the pipe, s, as already described in the explanation of the previous figure. There is now no means of ascertaining what progress was made in introducing Newcomen's engine into practice. Bradley incidentally mentions one belonging to a Mr. Louder, of Newhaven, which was a considerable improvement on Savery's invention. The same writer describes one made by the late Mr. Savery, and erected by the inventor about 1712 for "that curious gentleman Mr. Balle, at Cambden-house, which has succeeded so well, that there has not been any want of water since it has been built; and for the improvement of the curious" he gives a design of it," which he thinks the truest-proportioned of any about London:" this formsthe subject of the engraving (marked SAVERY, M.), "b, a boiler containing 39 gallons, e, a receiver holding 13 gallons; the pipe, g, from the surface of the water to the engine-tree, f, is 16 feet, which is the length that it sucks the water, but it may be made to draw the water 28 feet; the enginetree, up to the great cistern which receives the water, is 42 feet, but might be a hundred feet high if such a quantity of steam be allowed as is proportionable to the length of the pipe. The diameter, as well of the sucking pipe, g, as of the force pipe, l, is 3 inches; of the steam pipe, d, about an inch. When this engine begins to work, you may raise four of the receivers full of water in one minute, which is 52 gallons, and at that rate in an hour's time may be flung up about 3120 gallons, which is above 6 barrels or if there were two receivers, one to suck while the other discharged itself, as has been practised, we might raise 6240 gallons in the same time. The prime cost of such an engine is about 50 pounds, and the quantity of coal required for each working is about half a peck, so that the expense will be very trifling in comparison to what the carriage of water upon horses would amount to; and in such countries where wood is plenty, would amount to much less." Some of these machines were erected of considerable dimensions. For Bradley* further informs us that he had seen an engine, with two receivers, which held each of them a barrel (36 gallons) of water, which would furnish so great a quantity that P. 178, vol. ii. New Improvements of Planting and Gardening, both philosophical and practical, by Richard Bradley, F.R.S. 1718. even some tolerable large fountaine were supplied by it*. The action of this mechanism being precisely the same as that which has been described before, it will hardly be necessary again to explain its operation: b, is the boiler, n, funnel to supply it with water, c, handle of cock, which shuts off and admits steam, d, pipe connecting receiver, e, and boiler, f, a box or engine-tree connecting the rising and eduction pipes; o, reservoir. In this it will be seen the condensation is produced by water falling on the outside of the receiver as described in the MINERS' FRIEND. For the next important improvement, on the same part of the machine, we are indebted to a boyish love of idleness and play. "It was usual to work with a buoy in the cylinder, enclosed in a pipe, which buoy rose when the steam was strong, and opened the injection pipe, and made a stroke, whereby they were only able from this imperfect mechanism to make six or eight strokes in a minute, till a boy named Humphry Potter, who attended the engine, added what he called a scoggant, a catch that the beam or lever always opened, and then it would go fifteen or sixteen strokes in a minute." *P. 179, vol. ii. Ibid. + Scog, a term in use in the north of Scotland for that part (made with hair) of fishing tackle to which the hook is fastened. Scogie, a drudge. Another derivation has been suggested from to scog, to hide or secrete. He's scugging is a phrase for one avoiding his pursuers: A correspondent in the Mechanics' Magazine, p. 154, says, that to be found scogging, to be a scogger, are terms in very common use in the north of Yorkshire, and convey exactly the meaning of the terms, to be found skulking, to be a skulker. By a slight corruption Scoggan, as the operation which is performed enabled the boy to be scogging instead of attending to his business. P. 178. vol. ii. Desaguliers' Exper. Philos. |