582

HISTORY OF ENGINEERING.

Rook 1 .

water, stopping and screwing up the broken end, as also the touch-hole, and making aconstant fire under it: within twenty-four hours it burst and made a great crack ; thushaving a way to make my vessels, so that they are strengthened by the force within them,and the one to fill after the other, I have seen the water run like a constant fountain stream40 feet high ; one vessel of water rarified by fire driveth up 40 of cold water : and theman tliat tends the work is but to turn two cocks, that one vessel of water being consumed,another begins to force and refill with cold water, and so successively ; the fire beingattended and kept constant, which the self-same person may likewise abundantly performin the interim between the necessity of turning the said cocks.” The Marquis called thisa semi-omnipotent engine, and says he intended to have a model of it buried with him.

Sir Samuel Morland , in the year 1683, exhibited to Louis XIV . some new principles onthe power of fire, by “ which when water is evaporated, it will acquire a space equal to 2000times what it was before; and that in such a state it might be made highly useful forraising water.”

In the Philosophical Transactions for 1697 is a notice of a method for draining mines,where there is not the conveniency of a near river to play an engine, with air-pumps andcylinders connected by an air-pipe; which no doubt refers to the inventions of Denis Papin , a Frenchman, who first showed that a piston working tight in a cylinder might beraised by boiling a little water under it, and that by cooling and condensing the vapourwhich had raised it, a vacuum would be formed below, when the atmospheric pressurewould force it down.

The first engine applied in England to practical purposes was made by Thomas Savery ,for which he obtained a patent in the year 1698; and he suggested that it could be usedfor working mills, raising water to houses for domestic purposes, and extinguishing fires,supplying cities with water, draining fens and marshes, propelling ships, &c. This engine,though so highly creditable to the genius of its inventor, had some considerable defects,particularly in its application to the drainage of mines, the depths of which had been greatlyincreased; rendering it highly desirable that some process of working them, less expensiveand difficult than that ordinarily adopted, should be resorted to.

The lift of Savory’s engine was limited to 90 feet perpendicular, so that to raise waterfrom the bottom of a mine it was necessary to place one at every 90 feet of depth ; thewater being successively raised into reservoirs, one above the other. It was also foundthat sufficient strength could not be given to an engine of this description, when made upona large scale, and that the consumption of fuel was very great.

Thomas Newcomen , a blacksmith at Dartmouth , and John Cawley, a plumber of the sameplace, endeavoured to overcome the defects in Savery ’s engine, and to them we are indebtedfor the first atmospheric engine, for which they took out a patent in 1705. Here the pistonwas pressed down in a cylinder by the atmospheric pressure, a vacuum being previouslyformed below the piston, by filling the space with steam, which was then condensed. Inthis engine there were three principal parts; the boiler, which generated the steam, thecylinder, in which the steam was condensed, and the beam, whose movements followed thealternate admission and condensation of the steam, communicating the motion to therod of the pump. An engine of this construction raised a load of 7 or 7J pounds forevery square inch of the surface of the piston.

This engine, which soon came into general use, received several improvements fromMr. Beighton, an engineer, who fixed a rod to the beam, called a plug-frame, with pins orcatches in it, which opened and shut the valves with great precision and regularity ; so thatno attendant was required for that purpose, and the engine thus worked itself. Thecelebrated John Smeaton also applied all his knowledge in mechanic* to proportion thevarious parts, which enabled him to construct machines of greater power, and to performmore work with the same amount of fuel. A crank and fly-wheel was added, which, fromthe reciprocating vertical motion of the piston, produced a continued circular motion.

The atmospheric engine had considerable advantages, arising from the almost unlimitedpower which could be commanded, which depended on the range of surface of the piston,from the low degree of temperature and pressure at which the steam was produced, sothat there was little risk of explosion, from the simple mode by which the steam wascondensed, and from the power which the engine possessed of opening and shuttingits valves.

It had also its disadvantages, arising from the alternate heating and cooling of thecylinder, during which process a considerable quantity of steam was lost, and the airrushing in whilst the piston was under atmospheric pressure.

Newcomen ’s was, however, the first really efficient steam-engine applied safely and pro-fitably to many very important purposes, and no doubt to it Mr. Watt was indebted formany valuable suggestions; it was exclusively used for sixty years, and, according to Mr.Carr, was the chief hydraulic engine for upwards of an hundred. In the coal mines itwas universally adopted, as it was also in those of Cornwall , Cumberland, and elsewhere.

The great improvements made in the steam-engine by Mr. Janies Watt were condensing