for, during the term of his patent, it does not appear that he availed himself of the security arising from the use of * * Various Papin's Saftely Valve. * attempts were made to strengthen the boilers, by radiating arms fixed in the inside, but without any successful result: so that, at this period, the only use to which Savery's apparatus could be applied with safety, was to raise water to heights not exceeding 30 or 32 feet-a virtual abandonment of its pretensions as a mine-draining power, which was the grand object of all Savery's exertions."

Then came the improvements of Newcomen the blacksmith, and Cawley the glazier, who "made the experiment of introducing steam under a piston moving in a cylinder and formed a vacuum, by condensing the steam by an effusion of cold water on the outside of the steam-vessel; so that the weight of the atmosphere pressed the piston to the bottom of the cylinder. This was the first form of the atmospheric-engine, the simplest and most powerful machine that had hitherto been constructed."

Still many inconveniences remained to be removed; and not the least was the necessity of employing boys, or men to open and shut some of the cocks; for although the risk of accident from the explosion of the boiler might now be considered as obviated, yet the effect of the engine depending much on the condition of its parts, and these being rarely deranged by slight irregularities in their action, the danger of injury to the machine itself was considerably increased from the ignorance or carelessness of the attendants.

The mechanism for opening and shutting the cocks also remained perplexed by latches and strings until Mr. Henry Beighton, an engineer, extensively employed in the construction of machinery, erected an engine at Newcastle-on-Tyne in 1718, in which all these "cock-boys" and complication of cords were superseded by a rod suspended from the beam which operated as a mechanism invented by him called hand-gear; a contrivance, with some slight modifications, employed in engines of the present day. It would also appear that the steel

yard safety-valve was first used in the boiler of this engine, having been suggested to Beighton by Desaguliers.

Mr. Stuart's description of Beighton's engine we shall quote at length; as it will not only give our readers a complete idea of its most approved form of construction at that period, but show more clearly the value of the improvements introduced by that ingenious engineer.

For the use of the illustrative engravings, we are indebted to the kindness of Mr. Stuart, whose ability as a draughtsman is not the least of his merits.

"The cylinder of the Griff Engine was 22 inches in diameter; and Beighton calculated that it contained 113 gallons of steam at every stroke, equal to about 14,464 gallons per minute, which was produced from about five pints of water; and this quantity was equal in its performance to three-fourths of the atmospheric pressure; so that, making allowance for the friction* of the piston, levers, and other parts, about eight pounds of water was raised by each square inch of the piston.

"In examining the seventeenth (our first) figure, which is a view of the Atmospheric Engine as improved by Beighton, it will be seen, that, in addition to the hand-gear, he gave a better arrangement and form to the parts already in use, and paid more attention to the proportion of the parts among themselves, and to the work which they had to perform; besides introducing greater neatness and accuracy of workmanship into his engines than had been attempted by his predecessors.

"In the seventeenth figure, the cistern, x, for the supply of injection water, is placed as in the previous engravings, and water is pumped into it by a small pump connected with the pipe y y, leading from the mine. (The lever 'beam,, is not continued on the pump side beyond its axis A, as this would have required our figure to have been drawn on a scale much too small for air-tight, a ring or piece of match† is being distinct.) To make the piston, d,

"Tallow was used in these engines to lessen the friction, but not to keep them air-tight."

+"The origin of packing the piston is thus given by Desaguliers: Having screwed a large broad piece of leather to the piston which turned up the sides of

laid upon its circumference; which is kept moist by a small stream of water kept constantly running from the pipe, s, upon the piston d: a projecting rin rising above the highest point to which the piston is elevated, prevents the water from flowing over the sides of the cylinder, when the piston has reached its upward stroke. The boiler which is shown as cased in brick-work, is supplied with warm water from this rim by a pipe b; the water falls into a funnel attached to a pipe g, which rises to a convenient height above the top of the brick-work, and descends about a foot into the water in the boiler; the two gauge-pipes i i, are used (as in Savery's Engine) to ascertain the quantity of water in the boiler; the lower end of one is immersed for a short distance in the water-the lower end of the other reaching to within a few inches of its surface. If steam issues from both cocks when they are opened, there is a deficiency of water in the boiler; if both give water, then it shows there is an over-abundant quantity. The cold water is injected into the cylinder through a pipe f; and after it has performed its office of condensation, it is conducted by the pipe tt, and escapes through a valve at its extremity into the well or reservoir. When the water which flows from s, on the top of the piston, is not all used to supply the waste of evaporation in the boiler, its accumulation would soon fill the rim or cup above the piston, and flow over its edge upon the casing of the boiler. To prevent this overflow, a pipe u u, is inserted at a, which allows the accumulated quantity to fall into the well. The air which is contained in the injected water, and produced by the condensation of the steam under the piston, escapes by a small pipe w, to which is attached a little cup, with a valve opening outwards: when the air is expelled by the descent of the piston, it is shut by the pressure of the

the cylinder two or three inches, in work. ing it wore through, and cut that piece from the other, which, falling flat on the piston, wrought with its edge to the cylin der, and, having been in a long time, was worn very narrow; which being taken out, they had the happy discovery, whereby they found that a bridle-rein, or even a soft thick piece of rope, going round, would make the piston air and water-tight.' -Desaguliers' Nat. Phil. Hornblower observes, 'We need not say any thing to the practical engineer about leathering a steam piston. Nor is it necessary to comment on the Doctor's acquaintance with steam and leather in contact.'-Gregory, Mech. vol. ii. p. 358. 1st edition."

atmosphere; a small quantity of water is occasionally introduced by the pipe n, to keep it air-tight. This is called the snifting-valve, because the air makes a noise every time it blows through it, like a man snifting with a cold.'

"With the exception of the position of this valve, which Newcomen supplied by the pipe used for conveying the water produced by the condensation of the steam into the well, all the parts that we have particularized have the same operation with those similarly placed in the previous figures. The hand-gear contrived by Beighton, is shown in the eighteenth (our second) figure, on a larger scale than in the preceding engraving, for the purpose of giving a clearer view of its construction and action. The Atmospheric Engine, by its introduction, first properly became a self-acting apparatus.

"Between two perpendicular pieces of wood (not to confuse the figure, one only, B, is shown) there is a square iron axle, o, which has upon it four iron pieces subservient to the turning of the regulator, by shooting forward and drawing back the fork m m, fastened to the handle, V V, of the regulator T. In the perpendicular working beam, called by Beighton the plug-frame, there is a slit, which is contrived so that its pins work on the fore part, middle, and back part, to raise and depress the levers, xyz, that move the iron axle o, as much round as is necessary. On the iron axle is fixed a piece called the Y, from its resemblance to that letter, with a moveable weight r, fixed on its upper end. The stirrup, N, is fixed to the hooks ss, suspended on the iron axle; the levers or spanners are also fixed upon this axle, at right angles to the Y piece. The handle of the horizontal fork has holes near its extremity, for the purpose of keeping any part of the end a, in any part of the regulator lever V v, which moves on a horizontal bar between the pins t a.

"From the situation of the apparatus, the regulator is partly open, which is apparent from the shifting plate or valve, shown by the dotted line x, being turned from under the throat-pipe s, which communicates with the cylinder: the situation of the piston in the cylinder will be somewhat higher than shown in the seventeenth figure, consequently the lever-beam and the plug-frume are nearly at their greatest elevation; and the pin or pulley 2, in the slit of the plug-frame, has so raised the lever or

spanner p, that the weight of the head of the Y piece is brought so far from under n, as to have past the perpendi cular to the axle; and being ready to fall over towards m, its shank D, 'will strike the pin 4, of the stirrup, with a smart blow, and drawing the fork m m, horizontally towards the plug-frame, will also draw the end, o, of the handle of the regulator (which slides on the bar between t and a), and thereby shut off the communication between the cylinder and the boiler. The fall of the plug-frame will reverse this motion. The moment this movement is completed, the pin 3, on the outside of the plug-frame, depresses the lever, x, attached to the quadrant of a wheel g, which moves another quadrant f, which is fixed on the axis or spindle of the cock, e, of the injection-pipe bc. This, admitting cold water into the cylinder, condenses the vapour, and produces a vacuum; and the pressure of the atmosphere carries the steam-piston downwards, "and raises the plug-frame. The lever, x, is raised by another pin, which shuts the injection-cock, and depressing one of the spanners fixed on the iron axle, moves the stirrup and fork into the position which opens the sliding valve, and permits the steam again to issue from the boiler into the cylinder.

"The nineteenth (our third) figure is a geometrical view of the same engine, slightly varied in some of its details, and which on the whole may be considered as improvements. As its action is the same as those we have already described, an enumeration of the names of the parts will be sufficient to explain their uses. H is the fire-place under the boiler W; ii are the two gauge-cocks; o, the spindle of the regulator valve, which opens or shuts the communication between the cylinder and boiler by the throat-pipe e; the pipe tt carries the heated injection water into the well; from this pipe, a small branch g proceeds with a funnel-cup, having a valve opening upwards; the hot injection water passes from this into the boiler, and an additional supply is procured by the pipe b, from the cup containing the water used to make the steam-piston airtight; rr is the plug-frame; pp, the spanners, moving the fork, and lever of the regulating valve o, which is coustructed somewhat differently in this from the preceding figure; m is the tumbling bob, which has the same use and operation as the Y piece, The injection-cock k is moved by a similar contrivance of a fork acting on the end of a lever, and which is put in action by pins fixed in the plug-frame, to move the