ENGINE, .for raising water. The frame of the machine is of cast iron, nearly in the form of the letter A ; there are two of these frames, B B, (fig. 1, Plate Pump Engine,) screwed together by means of five wrought iron pillars, a a a a; 1) is another smallerframe, to support the axis 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, f f, 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, f f, 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,f f, by two nuts, and go down into the pumps, G H, sup ported from the iron frame by eight iron braces, Ix 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 ofthe 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 3i inches diameter, and 8 inches stroke. As the two cranks, b, b, 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 about 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 ld of an inch 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 down the slope of a hill 200 fathoms long\, 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.