ENGINE. 



of the fly wheel, connected with the other 

 frame by three short pillars; E, is the fly 

 wheel, turned by winches on the end of 

 its axis; it has a pinion (13) of 13 leaves 

 upon its axis, turning a wheel (48) of 48 

 teeth, on whose axis are two cranks b, b, 

 opposite to each other, to work the 

 pumps : e e, are the two crank rods, made 

 each in two branches, and jointed at the 

 lower end into two other rods,//, which 

 slide through holes made in the fixed 

 bars, gg, fig. 2; the crank rods receive 

 these bars between their two branches, 

 and by this means, though the rods, //, 

 are confined by their guides to move 

 truly vertical, the crank rods, e e, can 

 partake of the irregular motion of the 

 crank. The pump rods of the pumps 

 are screwed to the rods,//, by two nuts, 

 and go down into the pumps, G H, sup- 

 ported from the iron frame by eight iron 

 braces, h h. The pumps consist of two 

 barrels, G H, with valves at the bottom, 

 allowing water to enter them freely, but 

 preventing its return ; the buckets fixed 

 to the pump rods fit the barrels truly, and 

 have valves in them shutting downwards ; 

 I, is a chest bringing water to the valves 

 in the bottom of the barrels ; K, is another, 

 communicating with the top of the bar- 

 rels by two crooked passages, to carry 

 away the water from them ; the barrels 

 are close at top, and the pump rods pass 

 through close stuffing boxes, through 

 which no water will leak by them. The 

 action of the pump is the same as the 

 common sucking pump : when the bucket 

 is drawn up, the valve in it closes, and it 

 forms a vacuum in the lower part, of the 

 barrel; this causes the water to ascend 

 into it through the chest, I, to restore the 

 equilibrium ; at the same time it raises all 

 the water which was above it through the 

 chest, K ; on the descent of the bucket the 

 valve at the bottom of the barrel shuts, 

 and prevents the escape of the water; the 

 valve in the bucket opens, and the water 

 passes through it, ready to be raised at 

 the next stroke. The barrels in ques- 

 tion are 3J inches diameter, and 8 inches 

 stroke. As the two cranks, 6, 6, are op- 

 posite each other, when one bucket is 

 rising, the other is going down ; by this 

 means the power required to turn the 

 machine by the handles is equalized, and 

 also the quantity of water raised by the 

 engine. 



Engines for raising water, by the pres- 

 sure and descent of a column inclosed in 

 a pipe, have been lately erected in dif- 

 ferent parts of the country. The prin- 

 ciple now adverted to was adopted in 



some machinery executed in France abou' 

 1731, and was likewise adopted in Corn- 

 wall more than forty years ago ; but the 

 pressure engine, of which we are about 

 to give a particular decription, is the in- 

 vention of Mr. R Trevithick, who pro- 

 bably was not aware that any thing at all 

 similar had been attempted before. This 

 engine, a section of which, on a scale of 

 id of an hich to a foot, is shewn in Plate 

 Pressure-Engines; one was erected about 

 eight years ago at the Druid copper mine, 

 in the parish of Illogan, near Truro. A B, 

 represents a pipe six inches in diameter, 

 through which water descends from the 

 head to the place of its delivery, to run 

 off by an adit at S, through a fall of 34 

 fathoms in the whole ; that is to say, in a 

 close pipe ^Lown the slope of a hill 200 

 fathoms longy with 26 fathoms fall; then 

 perpendicularly six fathoms, till it arrives 

 at B, and thence through the engine from 

 B to S two fathoms ; at the turn B, the 

 water enters into a chamber, C, the lower 

 part of which terminates in two brass 

 cylinders, four inches in diameter ; in 

 which two plugs or pistons of lead, D 

 and E, are capable of moving up and 

 down by their piston rods, which pass 

 through a close packing above, and are 

 attached to the extremities of a chain 

 leading over and properly attached to the 

 wheel Q, so that it cannot slip. 



The leaden pieces, D and E, are cast 

 in their places, and have no packing what- 

 ever. They move very easily; and if at 

 any time they should become loose, they 

 may be spread out by a few blows with a 

 proper instrument, without taking them 

 out of their place. On the side of the two 

 brass cylinders, in which D and E move, 

 there are square holes communicating 

 towards G, with a horizontal trunk, or 

 square pipe, four inches wide, and three 

 inches deep. All the other pipes, G, G, 

 and R, are six inches in diameter, except 

 the principal cylinder wherein the piston, 

 H, moves ; and this cylinder is ten inches 

 in diameter, and admits a nine foot 

 stroke. 



The piston rod works through a stuf- 

 fing-box above, and is attached to M N, 

 which is the pit rod, or a perpendicular 

 piece divided into two, so as to allow its 

 alternate motion up and down, and leave 

 a space between, without touching the 

 fixed apparatus, or great cylinder. The 

 pit rod is prolonged down in the mine> 

 where it is employed to work the pump ; 

 or, if the engine was applied to mill-work, 

 or any other use, this rod would be the 

 communication of the first mover, K L, 



