The piston being at the top of the cylinder, as shown in the Figure, let steam be admitted into the cylinder till it is full. When this is done, turn the cock D to prevent the entrance of any more, and open the cock F, to allow cold water from G to flow into the outer cylinder ZZ. By cooling the steam cylinder A, this will condense the steam within it, which will form a vacuum under the piston S. The whole weight of the atmosphere, which now presses on the upper side of the piston, having no force on the other side to counterbalance, it will force the piston S down to the bottom of the cylinder. By this means, the end I of the great beam is depressed, and the opposite end I' raised, so as to work the pump L, and raise the water which it contains. When the piston has reach ed the bottom of the cylinder, the cock F is shut, and the cock E opened, and the water in the outer cylin der ZZ, descends into the well 0, while the small quantity formed by the condensation of the steam in A, descends also into 0 through the pipe P. By means of a counter-weight M, placed on the rod K, the piston S is brought up to the top of the cylinder, and steam being again admitted, and again condensed as already described, the piston is again forced down, and a fresh draught of water brought from the well L. The fire beneath the boiler is shown at N, the ash-pit at W, the flues at XX, and the pipe which supplies the re servoir G at TT. The mouth of the well or mine to be drained, is shown at L, and H is a pipe for admit ting water above the piston, to keep it water-tight.
Such was the state of the atmospheric engine before March 1712, when the patentees, as above stated, ob tained such important aid from the Birmingham artists. But an accident now occurred which turned out of great importance. Having observed the engine perform several strokes in very quick succession, they found, upon a strict examination, that there was a hole in the piston, which let the cold water in to con dense the steam in the inside of the cylinder, whereas this had always been done on the outside. Hence arose the use of the injection pipe, which was after wards made to squirt a jet of water upwards from the bottom of the cylinder into the steam which it con tained. The outer cylinder ZZ, was therefore no longer necessary, and the pipe f entered the bottom of the cylinder, as shown in Fig. 5.
Dr. Desaguliers remarks, " that they used to work with a buoy in the cylinder, enclosed in a pipe, which buoy rose when the steam was strong, and opened the injection, and made a stroke, thereby they were capa ble of only giving six, eight, or ten strokes in a minute, till a boy, I Iumphry Potter, who attended the engine, added (what he called scoggan,) a catch, that the beam Q always opened, and then it would go fifteen or sixteen strokes in a minute. About this time (in 1713) the leathering of the piston was found out by ac cident. " Having then screwed a large broad piece of leather to the piston, which turned up the sides of the cylinder two or three inches; in working it wore through, and cut that piece from the other, which fall ing flat on the piston, wrought with its edge to the cylinder, 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 or match going round, would make the piston air and water-tight." A few years afterwards, in 1717, Dr. Desagulicrs communicated to Mr. Beighton the use of the steel yard safety valve.
Notwithstanding these great improvements, the mechanism of the steam engine was still very imper fect. The necessity of cock buoys to open and shut the cocks, and the number of catches and strings em ployed gave a character of complexity to its parts, which rendered them liable to derangement from the slightest irregularity. All this apparatus, however, was superseded in 1818, by the invention of what is called hand-gear, which Mr. Henry Beighton, an able engineer, first applied to an engine which he erected at Newcastle-upon-Tyne. In this engine, the cocks were all opened, and that by the hand-gear, which was put in motion by a rod suspended from the main beam. Mr. Beighton made also several other changes upon the engine, which improved the form and arrange ment of its parts, and he introduced a neatness and ac curacy of workmanship unknown to his predecessors.
The steam engine as constructed by Mr. Beighton, is shown in Plate DV. Fig. 6, where h h is the great beam, C the cylinder, A the fire, and B the boiler, all - of which act in the manner already described. The part which we intend principally to describe, is the working perpendicular beam QQ, with all its machi nery for opening and shutting the regulator and injec tion cock. This machinery is contained within the compass of the letters D dC6P 5 4 1 Q N F E, but its parts are here on such a small scale, that we have given them separately in Fig. 7. Between two per pendicular pieces of wood on each side of P, Fig. 6, and marked AB in Fig. 7, there is a square iron axis AB, which carries four iron pieces necessary for turn ing the regulator, by pushing forward and drawing back the fork fastened to the handle of the regulator Fig. 6, and marked QOEL, Fig. 7. In the beam QQ, there is a slit so contrived that its pins work on the fore part, middle, and back part, to raise and depress the levers 5, 4, that move the axle AB, as far about its centre as is necessary. A piece CED called the Y moves round AB on an axis, and carries a weight F, which by means of a key and wedge can be slipped along the arm C. By means of a hooked stirrup GLE, the axle AB is joined to the horizontal fork ON. A spanner or handle G 4 is driven on upon the axle AB ; and another shorter spanner H 5, at half right angles to this, is forced on to where it is made fast. When the working beam QQ rises, the pulley p will lift up the spanner LI 5, which turns the axle AB so far round as to throw the Y, CED with its weight F from C to 6, in which direction, after passing the per pendicular, it would continue to move towards 0, if it were not stopped by a strap of leather fixed to its top at CF., and made fast at the points m, n, in such a manner as to allow the Y to vibrate about a quarter of a circle in falling forwards and backwards after it has passed the perpendicular. The horizontal fork ON is joined at its end 0 to the spanner or handle of the re gulator P 9 Q 10, there being several holes in these pieces, that any part of the end 0 may be kept in any part of the slit in the spanner, as may be necessary for the better motion of the two pieces. The other end N of the fork is fastened to the bottom EKNL of the stirrup by the long horizontal pin L, so that the fork may continue horizontal as it is pushed forward and drawn back by the spanner P 10, to shut and open the regulator in the manner to be afterwards described. There is a horizontal piece u / so placed that the end 10 of the spanner may bear upon it, and be supported as it slides backwards and forwards.