Savery next endeavoured to bring his invention into practical use, but this was a matter of much greater difficulty. So many schemes with a like object had been brought out and failed, that the mining interest came to regard new projects with increasing suspicion. To persuade them that he was no mere projector, but the inventor of a practicable working engine, Savery wrote and published his ‘Miner’s Friend.’ “I am not very fond,” he there said, “of lying under the scandal of a bare projector, and therefore present you here with a draught of my machine, and lay before you the uses of it, and leave it to your consideration whether it be worth your while to make use of it or no.”
Inventors before Savery’s time were wont to make a great mystery of their inventions; but he proclaimed that there was no mystery whatever about his machine, and he believed that the more clearly it was understood, the better it would be appreciated. He acknowledged that there had been many pretenders to new inventions of the same sort, who had excited hopes which had never been fulfilled; but this invention which he had made was a thing the uses of which were capable of actual demonstration. He urged that the old methods of raising water could not be carried further; and that an entirely new power was needed to enable the miner to prosecute his underground labours. “I fear,” said he, “that whoever by the old causes of motion pretends to improvements within the last century does betray his knowledge and judgment. For more than a hundred years since, men and horses would raise by engines then made as much water as they have ever done since, or I believe ever will, or, according to the law of nature, ever can do. And, though my thoughts have been long employed about water-works, I should never have pretended to any invention of that kind, had I not happily found out this new, but yet a much stronger and cheaper force or cause of motion than any before made use of.” He proceeded to show how easy it was to work his engine,—boys of thirteen or fourteen years being able to attend and work it to perfection after a few days’ teaching,—and how he had at length, after great difficulty, instructed handicraft artificers to construct the engine according to his design, so that, after much experience, said he, “they are become such masters of the thing that they oblige themselves to deliver what engines they make exactly tight and fit for service, and as such I dare warrant them to anybody that has occasion for them.”[31]
SAVERY’S ENGINE.
Savery’s engine, as described by himself, consisted of a series of boilers, condensing vessels, and tubes, the action of which will be readily understood with the help of the annexed drawing.[32]
Its principal features were two large cylindrical vessels, which were alternately filled with steam from an adjoining boiler and with cold water from the well or mine out of which the water had to be raised. When either of the hollow vessels was filled with steam, and then suddenly cooled by a dash of cold water, a vacuum was thereby created, and, the vessel being closed at the top and open at the bottom, the water was at once forced up into it from the well by the pressure of the atmosphere. The steam, being then let into the vessel from the top, pressed upon the surface of the water, and forced it out at the bottom by another pipe (its return into the well being prevented by a clack), and so up the perpendicular pipe which opened into the outer air. The second vessel being treated in the same manner, the same result followed; and thus, by alternate filling and forcing, a continuous stream of water was poured out from the upper opening. The whole of the labour required to work the engine was capable of being performed by a single man, or even by a boy, after very little teaching.
Although Savery’s plans and descriptions of the arrangement and working of his engines are clear and explicit, he does not give any information as to their proportions, beyond stating that an engine employed in raising a column of water 3½ inches in diameter 60 feet high, requires a fireplace 20 inches deep. Speaking of their performances, he says, “I have known, in Cornwall, a work with three lifts of about 18 feet each, lift and carry a 3½-inch bore, that cost 42s. a day (reckoning 24 a day) for labour, besides the wear and tear of engines, each pump having four men working eight hours, at 14d. a man, and the men obliged to rest at least a third part of that time.” He pointed out that at least one-third part of the then cost of raising water might be saved by the adoption of his invention, which on many mines would amount to “a brave estate” in the course of a year. In estimating the power of his engine, Savery was accustomed to compare it with the quantity of work that horses could perform, and hence he introduced the term “horse power,” which is still in use.
Although, in the treatise referred to, Savery describes an engine with two furnaces, the drawing which he presented to the Royal Society showed only one; and it appears that in another of his designs he showed only one cylindrical vessel instead of two. In order to exhibit the working of his engine on a larger scale than in the model, he proceeded to erect one in a potter’s house at Lambeth, where, Switzer says, though it was a small engine, the water struck up the tiles and forced its way through the roof in a manner that surprised all the spectators. Switzer mentions other engines erected after Savery’s designs for the raising of water at Camden House and Sion House, which proved quite successful. The former, he says, was the plainest and best proportioned engine he had seen: it had only a single condensing vessel; and “though but a small one in comparison with many others of the kind that are made for coal-works, it is sufficient for any reasonable family, and other uses required for it in watering middling gardens.”[33] Four receivers full of water, or equal to 52 gallons, were raised every minute, or 3110 gallons in the hour; whilst, in the case of the larger engines with double receivers, 6240 gallons an hour might easily be raised. The cost of the smaller engine was about fifty pounds, and the consumption of coal about a bushel in the twenty-four hours, supposing it was kept constantly at work during that time.
HUEL VOR, WITH REMAINS OF THE OLD WORKS.