NEWCOMEN’S HOUSE, DARTMOUTH.
[By R. P. Leitch.][38]
The Newcomen family have long since become extinct in Dartmouth. They are said to have left the place long ago, and gone northward; but we have been unable to trace them. The Newcomens appear to have occupied a respectable position in Dartmouth down to about the middle of the last century. Their burying-place was in the north-side chapel of the fine old parish church of the town, where several tablets are erected to their memory. Amongst others, there is one to William Newcomin, Attorney-at-Law, who died the 24th of August, 1745, aged 57, supposed to have been a brother, and another of the same name, who died in 1787, aged 65, supposed to have been a son of the ironmonger.
Thomas Newcomen was a man of strong religious feelings, and from an early period of his life occupied his leisure in voluntary religious teaching. He belonged to the sect of Baptists; and the place was standing until recently in which he regularly preached. When he afterwards went into distant parts of the country on engine business, he continued to devote his Sundays to the same work. How he first came to study the subject of steam is not known. Mr. Holdsworth says a story was current in Dartmouth in his younger days, and generally believed, that Newcomen conceived the idea of the motive power to be obtained from steam by watching the tea-kettle, the lid of which would frequently rise and fall when boiling; and, reasoning upon this fact, he contrived, by filling a cylinder with steam, to raise the piston, and by immediately injecting some cold water, to create a vacuum, which allowed the weight of the atmosphere to press the piston down, and so give motion to a pump by means of a beam and rods.[39]
It is probable that Newcomen was well aware of the experiments of Savery on steam while the latter was living at Modbury, about fifteen miles distant. It will be remembered that Savery was greatly hampered in his earlier contrivances by the want of skilled workmen; and as Newcomen had the reputation of being one of the cleverest blacksmiths in the county, it is supposed that he was employed to make some of the more intricate parts of Savery’s engine. At all events, he could scarcely fail to hear from the men of his trade in the neighbourhood, what his speculative neighbour at Modbury was trying to compass in the invention of an engine for the purpose of raising water by fire. He was certainly occupied in studying the subject about the same time as Savery; and Switzer says he was well informed that “Mr. Newcomen was as early in his invention as Mr. Savery was in his, only the latter being nearer the Court, had obtained the patent before the other knew it; on which account Mr. Newcomen was glad to come in as a partner to it.”[40]
Another account[41] states that a draft of Savery’s engine having come under Newcomen’s notice, he proceeded to make a model of it, which he fixed in his garden, and soon found out its imperfections. He entered into a correspondence on the subject with the learned and ingenious Dr. Hooke, then Secretary to the Royal Society, a man of remarkable ingenuity, and of great mechanical sagacity and insight. Newcomen had heard or read of Papin’s proposed method of transmitting motive power to a distance by creating a vacuum under a piston in a cylinder, and transmitting the power through pipes to a second cylinder near the mine. Dr. Hooke dissuaded Newcomen from erecting a machine on this principle, as a waste of time and labour; but he added the pregnant suggestion, “could he (meaning Papin) make a speedy vacuum under your piston, your work were done.”
The capital idea thus cursorily thrown out—of introducing a moveable diaphragm between the active power and the vacuum—set Newcomen at once upon the right track. Though the suggestion was merely that of a thoughtful bystander, it was a most important step in the history of the invention, for it contained the very principle of the atmospheric engine. Savery created his vacuum by the condensation of steam in a closed vessel, and Papin created his by exhausting the air in a cylinder fitted with a piston, by means of an air-pump. It remained for Newcomen to combine the two expedients—to secure a sudden vacuum by the condensation of steam; but, instead of employing Savery’s closed vessel, he made use of Papin’s cylinder fitted with a piston. After long scheming and many failures, he at length succeeded, in the year 1705,[42] in contriving a model that worked with tolerable precision; after which he sought for an opportunity of exhibiting its powers in a full-sized working engine. It ought to be mentioned, that in the long course of experiments conducted by Newcomen with the object of finding out the new motive power, he was zealously assisted throughout by one John Calley, a glazier of Dartmouth, of whom nothing further is known than that he was Newcomen’s intimate friend, of the same religious persuasion, and afterwards his partner in the steam-engine enterprise.
Newcomen’s engine may be thus briefly described:—The steam was generated in a separate boiler, as in Savery’s engine, from which it was conveyed into a vertical cylinder underneath a piston fitting it closely, but moveable upwards and downwards through its whole length. The piston was fixed to a rod, which was attached by a joint or a chain to the end of a lever vibrating upon an axis, the other end being attached to a rod working a pump. When the piston in the cylinder was raised, steam was let into the vacated space through a tube fitted into the top of the boiler, and mounted with a stopcock. The pump-rod at the further end of the lever being thus depressed, cold water was applied to the sides of the cylinder, on which the steam within it was condensed, a vacuum was produced, and the external air, pressing upon the top of the piston, forced it down into the empty cylinder. The pump-rod was thereby raised; and the operation of depressing and raising it being repeated, a power was thus produced which kept the pump continuously at work. Such, in a few words, was the construction and action of Newcomen’s first engine.
It will thus be observed that this engine was essentially different in principle from that of Savery. While the latter raised water partly by the force of steam and partly by the pressure of the atmosphere, that of Newcomen worked entirely by the pressure of the atmosphere, steam being only used as the most expeditious method of producing a vacuum. The engine was, however, found to be very imperfect. It was exceedingly slow in its motions; much time was occupied in condensing the contained steam by throwing cold water on the outside of the cylinder; and as the boiler was placed immediately under the cylinder, it was not easy to prevent the cold water from splashing it, and thus leading to a further loss of heat. To remedy these imperfections, Newcomen and Calley altered the arrangement; and, instead of throwing cold water on the outside of the cylinder, they surrounded it with cold water. But this expedient was also found inconvenient, as the surrounding water shortly became warm, and ceased to condense until replaced by colder water; but the colder it was the greater was the loss of heat by condensation, before the steam was enabled to fill the cylinder again on each ascent of the piston.
Clumsy and comparatively ineffective though the engine was in this form, it was, nevertheless, found of some use in pumping water from mines. In 1711 Newcomen and Calley made proposals to the owners of a colliery at Griff, in Warwickshire, to drain the water from their pits, which until then had been drained by the labour of horses; but, the owners not believing in the practicability of the scheme, their offer was declined. In the following year, however, they succeeded in obtaining a contract with Mr. Back, for drawing the water from a mine belonging to him near Wolverhampton. The place where the engine was to be erected being near to Birmingham, the ironwork, the pump-valves, clacks, and buckets, were for the most part made there, and removed to the mine, where they were fitted together. Newcomen had great difficulty at first in making the engine go; but after many laborious attempts he at last partially succeeded. It was found, however, that the new method of cooling the cylinder by surrounding it with cold water did not work so well in practice as had been expected. The vacuum produced was very imperfect, and the action of the engine was both very slow and very irregular.