ENGINE. 



is a tumbler, or tumbling bob, capable of 

 being moved on the gudgeons, V, from 

 its present position to another, in which 

 the weight L, shall hang over with the 

 same inclination on the opposite side of 

 the perpendicular, and consequently the 

 end, K, will then be as much depressed as 

 it is now elevated. 



The pipe, R S, has its lower end im- 

 mersed in a cistern, by which means it 

 delivers its water without the posibility 

 of the external air introducing itself; so 

 that it constitutes a Torricellian column, 

 er water barometer, and renders the 

 whole column from A to S effectual, as 

 we shall see in our view of the opera- 

 tion. 



The operation. Let us suppose the 

 lower bar, K V, of the tumbler to be 

 horizontal, and the rod, P O, so situated, 

 as that the plugs , or leaden pistons, D 

 and E, shall lie opposite to each other, 

 and stop the water ways, G and F. In 

 this state of the engine, though each of 

 these pistons is pressed by a force equi- 

 valent to more than a thousand pounds, 

 they will remain motionless, because 

 these actions being contrary to each 

 other, they are constantly in equilibrio. 

 The great piston, H, being at the bottom 

 of its cylinder, the tumbler is to be 

 thrown by hand into the position here de- 

 lineated. Its action upon O P, and con- 

 sequently upon the wheel, Q, draws up 

 the plug E, and depresses D, so that the 

 water way, F, becomes open from A B, 

 and that of G to the pipe R : the water 

 consequently descends from A to C, 

 thence to F, until it acts above the piston 

 F. This pressure forces down the pis- 

 ton, and if there be any water below the 

 piston, it causes it to pass through G 

 G G into R : during the fall of the piston, 

 which carries the pit rod, M N, along 

 with it, a sliding block of wood, I, (dot- 

 ted) fixed to this rod, is brought into con- 

 tact with the tail, K, of the tumbler, and 

 lowers it to the horizontal position, be- 

 yond which it oversets by the acquired 

 motion of the weight L. 



The mere rising of the piston, if there 

 was no additional motion in the tumbler, 

 would only bring the two plugs, D and E, 

 to the position of rest, namely, to close 

 G and F, and then the engine would 

 stop ; but the fall of the tumbler carries 

 the plug, D, upwards, quite clear of the 

 hole, F, and the other plug, E, down- 

 wards, quite clear of the hole, G : these 

 motions require no consumption of power, 

 because the plugs are in equilibrio, as 

 was just observed. In this new situation 



the column, A B, no longer commufti 

 cates with F, but acts through G upon 

 the lower part of the piston H, and raises 

 it ; while the contents of the great cylin- 

 der above that piston are driven out 

 through F, and pass through the open- 

 ing at D into R. It may be observed, 

 that the column which acts against the 

 piston is assisted by the pressure of the 

 atmosphere, rendered active by the co- 

 lumn of water hanging in R, to "vvhich that 

 assisting pressure is equivalent, as has 

 already been noticed. When the piston 

 has ascended through a certain length, 

 another slide or block upon the pit-rod 

 (not seen) applies against the tail, K, of 

 the tumbler, which it raises and again 

 oversets, producing once more the posi- 

 tion of the plugs D E, here delineated, 

 and the consequent descent of the great 

 piston H, as before described. The de- 

 scent produced the former effect on the 

 tumbler and plugs, and in this manner 

 it is evident that the alternations will go 

 on without limit, or until the manager 

 shall think fit to place the tumbler and 

 plugs, D E, in the positions of rest, 

 namely, so as to stop the passages, F 

 and G. The length of the stroke may 

 be varied by altering the positions of the 

 pieces, I, and the other lower down, 

 which will shorten the stroke, the nearer 

 they are together ; as in that case they 

 will sooner alternate upon the tail, K, 

 As the sudden stoppage of the descent 

 of the column, A B, at the instant when 

 the two plugs were both in the water- 

 way, might jar and shake the apparatus, 

 those plugs are made half an inch shorter 

 than the depth of the side holes, so that 

 in that case the water can escape directly 

 through both the small cylinders to R. 

 This gives a moment of time for the ge- 

 neration of the contrary motion in the 

 piston, and the water in G G G, and 

 greatly deadens the concussion which 

 might else be produced. See STEAM; 

 ENGINE. 



Some former attempts to make pres- 

 sure engines upon the principle of the 

 steam-engine have failed ; because water, 

 not being elastic, could not be made to 

 carry the piston onwards a little, so as 

 completely to shut one set of valves and 

 open another; in the present judicious 

 construction, the tumbler performs the 

 office of the expansive force of steam at 

 the end of the stroke. 



ENGINE for driving piles, used at 

 building Westminster bridge, is con- 

 structed as follows : A, (Plate V. Miscel. 

 fig. 3.) is the great shaft, on which are 



