on the piston in this case amounted to 50 tons, or 58 lbs. per square inch, and the speed per minute multiplied by the weight lifted, and divided by 33,000, give 168 as the nett horse-power. Its average speed was four strokes; but it could, if necessary, be raised to seven strokes per minute, without causing any perceptible shock in the descending column. The piston rod worked through the bottom of the cylinder, and was directly connected with the pump rod, to which was attached a weighted plunger pole. In order to prevent impact, and secure smoothness of action, the water from the descending column was slowly admitted on the piston, and by a double system of valves brought to a gradual state of rest. Into a nozzle placed in front of the main cylinder were fitted inlet and outlet cylindrical valves. Right and left of these valves sluice valves were fixed for regulating the speed of the machine. Between the main cylinder and sluice valves were introduced two small 5-inch inlet and outlet piston valves. The cylindrical and piston valves received motion by a rod depending from a vibrating beam connected by a rod with the top of the main piston, and by cataract gearing placed beneath the valve nozzles. When the water was admitted to the main cylinder, the inlet cylindrical valve gradually opened, the stroke of the piston was then made to a given point, when the action of the cataract closed the valve, and, by displacing the 5-inch pistons, opened the apertures so as to allow the water to be continued from the column to terminate the stroke. When this was done similar movements occurred in the outlet valve and piston. The valves were made of brass, with a thin feather-edged beat, and kept tight by a boss projecting from the nozzle into which packing was inserted, and pressed down by a projection in the under surface of the valve bonnets. The water thus acted on the outer surface of the valves, between the zone of packing and the seatings, and when opened passed through the latter. The Alport engine ceased working in 1852; but its performance was so satisfactory, that the Talargoch Adventurers were induced, in 1843, to erect a similar machine at their mines, where it still continues to work.

For smaller machines, Mr. Darlington has adopted a different construction. His most recent engine is represented in the frontispiece; the sectional elevation at the end of the volume represents an engine designed in 1851 for a mine in Cornwall. The cylinder stands, in both cases, on two cast-iron bearers fixed across the shaft, the piston rod works through the cylinder bottom, and is a continuation of the pump rod. In front of the main cylinder is a smaller one with differential diameters for the admission and emission of water, and right and left are sluice

valves for regulating the speed of the engine. Connected with the second cylinder is a small 3-inch auxiliary cylinder, provided with inlet and outlet regulating cocks.

In starting this engine, the sluice valves and regulating cocks are opened, the water then flows from the pressure column, ▲, into the main cylinder, B, through the nozzle cylinder, &, and acts (see folding plate at end of volume) upon the piston, c, until the upstroke is completed. The piston, E, has a counter piston, E', of larger diameter, and when relieved from pressure on its upper surface, the water acting between them, forces it upwards, in which case the pressure is cut off from the main piston, and the water contained in the cylinder, B, is free to escape under the piston, E, through the holes in H. With the emission of the water the downstroke is effected. The downward displacement of the pistons, E and E', is performed by the auxiliary cylinder and pistons, F F', the pressure column is continually acting between these pistons, and by their alternate displacement by the fall-bob and canti-lever, K, on the arbor, L, the water is either admitted or prevented from operating on the upper surface of the piston, E'. The water from the top of piston, E', escapes through the apertures, I. The motion of the canti-lever, K, is effected by tappets fixed on the pump rod M.

One of these engines is now in operation at the Minera Mines in North Wales. The cylinder is 35 inches diameter; length of stroke 10 feet; pressure column 227 feet high. Its average speed is 80 feet, and maximum speed 140 feet per minute. The pressure of water on the piston is, 98 lbs. per square inch, giving a total weight on the piston of about 40 tons. This machine requires no personal attendance, the motion being certain and continuous as long as the working parts remain in order; consequently the cost of maintaining it is of the most trifling character.

The pressure of water has been ingeniously applied to rotary purposes by Mr. William G. Armstrong, of Newcastle-on-Tyne. His usual method is to fix the cylinders in an inclined position, and so to arrange them in pairs that the two may act upon one crank. This gentleman employs a kind of slide valve with an arrangement of escape or relief valves to avoid concussion of the pressure column at the turn of the piston's stroke. These engines have been successfully applied at the South Hetton Colliery and at a lead mine near Allenheads.

E

Fluids press equally in every direction; the weight of water is as the quantity, whilst the pressure exerted is in proportion to the vertical height; hence, if a vessel be filled by means of a vertical column or pipe, it will receive a pressure equal to the weight of the column multiplied by the number of times which the sectional area of the vessel exceeds that of the column employed.

Upon the foregoing principles depends the utility of the hydraulic press. Water is forced into the cylinder by means of a plunger, and repels the piston with a force proportionate to the number of times the piston of the ram exceeds that of the plunger.

In calculating the power of pressure engines, it must be borne in mind that it is only the vertical height of water which affords any power, and not the horizontal length of the column employed. In practice the pressure column will probably be laid on the side of a hill, and have nearly horizontal runs, so as to connect with the supplying reservoir; but it is only the perpendicular

*Rotary Engines.

height between the reservoir and piston of the engine which must be regarded as the element of power.

To find the load a Pressure Engine will lift in the shaft, and its horse-power:

Ascertain the vertical height of the column, and the pressure per square inch due to the height; multiply the nett area of the piston by the pressure per square inch, and deduct from the product, say, one-fifth for friction, which will give the number of pounds the engine is capable of lifting in the shaft; then multiply by the effective journey of the piston per minute, divide by 33,000, and the quotient is the horse-power.

Ex-The cylinder of a single-acting pressure-engine is 35 inches in diameter, the piston rod 7 inches in diameter, length of stroke 10 feet, number of strokes per minute 7 feet, the effective journey is therefore 70 feet, whilst the height of column is 232 feet. Required the load it will lift in the shaft, and the horsepower?

Area of cyl.

sq. in.

35 × 7854 = 962·1, less 7a × 7854 = 962·1—38·5 — 923·6 nett area of cylinder. 232 feet of pressure 100.7 lbs. s. per square in.; hence 923.6 x 100.7 93,006 lbs., gross pressure on piston, less for friction, 93,006-18,601 74,405 effective weight in Ibs., which the engine will lift in shaft. Then 74,405 × 70 ÷ 33,000 74,405 × 70

=

33,000

=

157.8 horse-power.

HYDROSTATIC PRESS.-To find the weight that a given power will raise :

Multiply the square of the diameter of the ram in inches by the power in lbs, and by the effective leverage of the pump-handle; divide the product by the square of the pump's diameter, also in inches, and the quotient is the weight the power is equal to.

Ex.-What weight will a power of 50 lbs. raise by means of an hydrostatic press, whose ram is 7 inches diameter, pump 3, and the effective average of the pump-handle being as 6 to 1? 72 × 50 × 6 72 × 82 × 50 × 6

=

=64 × 300 19,200 lbs. or 8 tons, 11 cwt.

TURBINES. Of late years these machines have attracted considerable attention, and the principle upon which they operate has been carefully investigated.

Some of the best turbines have been erected by M. Fourneyron, a French engineer, and by Messrs. Whitelaw and Stirrat, in Scotland. In America turbines have also been constructed of con

siderable excellence.

The turbines of M. Fourneyron consist of a horizontal water

wheel, the water entering at the centre and diverging in every direction towards the periphery. It then enters a series of buckets, and escapes at the circumference or external rim of the wheel. The water consequently acts on the buckets of the revolving wheel with a pressure proportionate to the vertical height of the fall. Mr. Whitelaw's machine is composed of hollow arms projecting from a central column, and each having a spiral direction. The principle of action is the same in all cases, the motion being produced from a centrifugal and tangential force caused by the weight of a column of water whose altitude is equal to twice the height of the fall due to the velocity of the water. In order to produce the greatest effect by the pressure and centrifugal force of the effluent water, the emission tubes must be so curved, that the apertures shall be in a right line with the radius of the wheel.

Experiment has shown that these machines are equally adapted for great and small falls, and that they work almost as effectually when submerged to a depth of six or seven feet as when free; they consequently make use of the whole of the fall when placed below water level. It is stated that from 70 to 78 per cent. of the theoretical power has been practically obtained from this arrangement.

The following general rule has been given by Mr. Whitelaw for computing the power of his turbine:

Multiply the effective flowing quantity of water in cubic feet per minute by the height of the fall in feet, and divide the product by 700; the result is the effect produced in horse-power.

Ex.-Required the power produced by a flow of 1,700 cubic per minute with a fall of 60 feet.

feet

PUMPS.-Pumps are known as plunger and lifting pumps. In Cornwall and most of the mining districts it is usual to make the working barrel somewhat smaller than the column, in order to obviate the friction which would occur if the latter were made of a less diameter than the former.

facility for changing the boxes.

This system also affords great

A bucket must never be raised more than 32 feet above the surface of the water, since the column at this height is nearly equal to the atmospheric pressure. From 9 to 12 feet is about the usual distance from the windbore to the bottom of the working barrel.

The power necessary to raise water to any given height is as its weight and velocity, with the addition of about one-fifth the whole power for friction. Therefore, multiply the velocity in feet by the perpendicular height of the water in feet, and by the