The water-ram, although it often figures in books on hydraulics, is less used than it ought to be: the reader generally regards it as a curious, old-fashioned device, and thinks no more of it; but for simplicity, cheapness, and useful effect combined, few machines are superior.

The merit of first employing the momentum of water to raise a portion of itself to a higher level is due to Mr. John Whitehurst, who, in a letter addressed to the Royal Society, in 1775, and printed in their Transactions, explains the principles of its action, and the mode of applying them, he had then successfully adopted.

M. Montgolfier, who does not appear to have known any anything of this communication, afterwards invented a similar machine in France, and gave it the name it still bears, " Le Bélier Hydraulique," from the butting action of the water; and Messrs. Boulton & Watt, with his permission, took a patent for it in England, dated December 13, 1797.

About twenty years later, the son of M. Montgolfier took an English patent for some improvements in his father's arrangements; and the visitors of the Great Exhibition of 1851 will remember two modifications of the hydraulic ram by London makers, Mr. Freeman Roe and Messrs. Easton & Amos.

The first machines made on the plan of the elder M. Montgolfier, by Messrs. Boulton & Watt, were exceedingly simple in their construction and arrangement, and yet very effective. A horizontal pipe, with a trumpet-shaped mouth to admit the water freely, was either inserted into the side of a supply-tank into which the stream flowed, and kept it full, or it passed through the dam into a reservoir that could be maintained at a uniform height. At the end of this pipe was a weighted valve, opening inwards, and upon the top of the pipe, near the end, was an air vessel, the capacity of it being at least equal to ten times the quantity of water to be raised at each stroke, and larger as the lift increased. At the bottom of the air-vessel was a valve, opening upwards, to admit the water into the air-vessel, and prevent its return, and to the air-vessel was attached the ascending-pipe, carrying up the water, raised to a higher level by the action of the machine.

The water being allowed to flow through the horizontal pipe, soon acquired velocity and force, and suddenly shut the valve at the end of the pipe; the momentum of the water,thus checked, lifted the valve in the air-vessel, forcing through

it a portion of the water, compressing the air within, and thus raising the water part way up the ascending pipe.

The force having been expended and the water brought to a state of rest, the weight-valve at the pipe end opened again; the descending column flowed through until its velocity again overcame the weight on the valve and forcibly shut it: thus, by repeated strokes, was the water raised to the top of the ascending pipe, and then every stroke discharged a volume of water inversely proportioned to the height.

The pipe conveying the descending water may be placed in an inclined position, instead of being laid horizontally; it is sometimes called the body of the ram, and the air-vessel and valves the head. M. Montgolfier considered, that with a well-constructed machine he might obtain 75 per cent. of useful effect; but the following were the results of experiment:

The fall of water was 3 feet 4 inches, the pipe, or body of the ram, 8 inches in diameter, and the height to which the water was raised, 15 feet 1 inch. The machine made 100 strokes in three minutes, expending in that time 67 cubic feet of water, and lifting 94 feet. Thus 67 x 3.33 = 223·11, 139.517 62

and 9-25 x 15·083 = 139.517.

per cent. of the power employed.

Then

or 62

The improvements of the younger M. Montgolfier consisted chiefly of the introduction of a "snifting valve," admitting a small quantity of air to make up the loss caused by absorption from the air-vessel by the ascending water, and of a contrivance to retain a "cushion or mattress of air" about the seat of the stop-valve, in order to lessen the concussion. (See Section, Fig. 39.) The following table shows the results obtained by French engineers.

The first column shows the head or fall of water acting on the machine; the second, the quantity expended. The third shows the height to which the water was raised; and the fourth the quantity raised to that height. The fifth column shows the useful effect in each case.

The quantities of water expended and raised are reduced to cubic feet, and the mean of useful effect is 605, or say six-tenths of the power expended: experiments also show that it can do good duty where it raises water seven times the height of the fall. Practically, perhaps one-half of the power expended, or 50 per cent. of useful effect will be the amount realised; for it must be expected that in all these experiments, the machines were in good order; yet there are many localities where a water-ram may be used with great benefit, as it steadily and constantly performs its task with very little care on the part of its owner, except to see that the water is strained through a grating, to keep back extraneous substances, and that the apparatus is protected or emptied during a hard frost. The first example mentioned raised 9 cubic feet, or 57-8 gallons in three minutes, amounting to 27,750 gallons in twenty-four hours, to a height of 11 feet 9 inches above the pond that supplied the water; and this without labour or expense, beyond the interest of its cost.

It is true that the heavy blow or shock, given by the momentum of the descending column, has hitherto limited the size of this apparatus; but this shock may be lessened by increasing the number and improving the form of valves and pipes; and the principle may probably be still further developed in the hands of skilful mechanics, as it has been successfully done in the pressure-engine.

After the foregoing passages had been written, the author was favoured with a letter and drawing from Messrs. Easton & Amos, of Great Guildford-street, Southwark, who exhibited one of their machines at the Crystal Palace; the drawing showing their mode of fixing it, to supply water to a mansion in the country.

They have made some improvements, for which they have taken a patent; and they state they can obtain a mechanical effect of 65 or 70 per cent.; that the lowest available fall is 2 feet, and the highest 35 to 40 feet; the quantity of water they lift varies with the size of the ram and height of the lift from half a gallon to 6 gallons per minute.

The greatest height to which they have raised the water, by a machine which has been at work some years, is 330 feet. They lay the "injection pipe," or body of the ram, at an inclination varying from one in eighteen for small falls to one in four for high falls. Having formed a dam across the stream, they take the water by an earthenware conduit-pipe

into a covered tank of brick-work; this receives the mouth of the inclined cast-iron pipe, which is opened or closed at pleasure by a flap valve; the pipe is laid in the ground below the reach of the frost, and the apparatus is fixed in a circular and domed vault of brick-work, which protects it from freezing; and from which the water that works the ram is conveyed by a covered channel to some convenient point where it may rejoin the stream at a lower level. The ram is secured to a stout piece of oak or elm timber built into the brick-work. (Fig. 39.)

To enable them to make a correct estimate of the size, capability, and cost of these machines, they require to know,1st. The number of feet fall to be obtained at the spring or brook to work the ram.

2nd. The perpendicular height from the lower part of the fall to the point where the water must be delivered.

3rd. The horizontal distance from the place of supply to the place where the water is wanted; and if the spring or stream be small, it is desirable to ascertain how many gallons it flows per minute.

CHAPTER XII.

CORN.-THE

THE APPLICATION OF WATER POWER TO GRIND
PROGRESS OF CORN-MILLS, AND DEVELOPMENT OF THEIR
MACHINERY.

IN applying water power to grind corn, the usual mode of computing the mill's capability is to ascertain the height and volume of the fall, and thence the available force, expressed in horses' power; and the wheel is so proportioned that when driven at the rate determined, the buckets may be about two-thirds filled by the average supply of water; in order to avoid waste at ordinary times, and also that during the excess in floods, an additional load in the buckets may compensate for the resistance of tail water.

It has been shown in the preceding pages that 12 cubic feet of water per second, or 750 pounds weight, are equal to an available horse's power, for each foot in height of their fall when acting by gravity on a well-constructed water wheel; that is to say, the useful mechanical effect is 73 per