to attend to that duty, when the performance is most necessary, namely, in a heavy gale, was put in practice with great success by captain Leslie, of the ship George and Susan, on a late voyage from Stockholm to North America. He fixed a spar aloft, one end of which was ten or twelve feet above the top of his pumps, and the other projected over the stern; to each end he athixed a block, or pulley; he then fastened a rope to the spears of the pump, and, after passing it through both pulleys along the spar, dropped it into the sea asteru. To the rope he fastened a cask, 110 gallons measurement, and containing Sixty or seventy gallons of water. This cask answered as a balance-weight, and every motion of the ship from the roll of the sea made the machinery work. When the stern descended, or when a sea or any agitation of water raised the cask, the pump-spears descended; and the contrary motion of the ship raised the spears, when the water flowed out. The ship was cleared out in a few hours, and the crew were of course greatly relieved.

In the Persian wheel, water may be raised by means of a stream d, plate IV, fig. 4, turning a series of floits, and furnished with buckets a b, suspended by strong pins fixed in the side of the rim; but the wheel must be made as high as the water is intended to be raised above the level of that part of the stream in which the wheel is placed. As the wheel turns, the buckets on the one side descend into the water, and then go up full on the other; when they arrive at C they strike against the end of the fixed trough and are overset, and empty the water into the trough; from which it may be conveyed in pipes to the place where it is designed for; and, as each bucket gets over the trough, it falls into a perpendicula position again, and goes down empty, until it comes to the water at 4, where it is filled as before. On each bucket is a spring, which, going over the top or crown of the bar, raises the bottom of the bucket above the level of its mouth, and so causes it to empty all its water into the trough.

Sometimes this wheel is made to raise water no higher than its axis; and then, instead of buckets hung upon it, its spokes are made of a bent form, and hollow within; these hollows opening into holes on the outside of the wheel, and also into those in the box upon the axis. So that, as the holes dip into the water, it runs into them; and, as the wheel turns, the water rises in the hollow spokes, and runs out in a stream from a series of holes, thus falling into the trough, whence it is couveyed by pipes to its destination.

tian era.

Nearly allied to the Persian wheel, but much more elegant in its contrivance, is the screw of Archimedes, a machine invented and used by this philosopher, for raising water and draining land in Egypt, about 200 years before the ChrisThe cochlion consists of a succession of buckets or recesses to be filled with the water to be raised; but instead of their being separate and detached, as in the Persian wheel, they are formed by the lower parts of the hollow thread of a screw, and their motion and succession are brought about by turning that screw,

This will be better understood by referring to fig. 5, which is a representation of this machine, and in which vu i shows a flexible tube or pipe, wound in a screw-like form round a solid cylinder yy, the two extreme ends of which are equipped with pivots, so that the cylinder, with its encircling screw-formed tube, may be made to revolve on its axis by the force of running water, or any other power applied to its upper or lower end. Lastly, this machme must be supported by its two pivots, so as to make an angle with the horizon, as shown in the figure. If now the lower end of the tube be supposed to be covered with water, that water will flow to its own level within the tube, and will occupy the lowest bend v; and if now the cylinder, yy, be turned round by its handle, in a direction from left to right, the lower end of the spiral tube will become elevated above the surface of the water in the reservoir, and that water which had entered into the tube will have no opportunity of escaping, but, by the motion of the screw-tube, will flow within it, until, at the end of the first revolution, it will be found in the second lower bend u. In the mean time the lowest extreme end of the tube will have made a second dip into the water of the reservoir, and will receive a second charge, which, in like manner, will be transferred to u, at the next revolution, while the water lately at u will be elevated to w; until at length, when the cylinder has made as many revolutions as there are turns of the tube round it, each lower bend will become filled with water, whatever may be the length of the cylinder yy; and as the extreme upper end a of the tube becomes depressed, in each revolution, into the situation of a lower bend, it will there discharge its water into an elevated cistern b, placed to receive it. The quantity of water raised by this machine will depend upon the capacity of the screw-pipe, and the angle above the horizon at which it is placed to work; but it will be seen by the figure, that there is room to dispose several pipes, parallel to each other, round the same cylinder, when they will all work simultaneously; or the whole cylinder itself may be made into a hollow screw, by merely placing a thin screw-formed diaphragm or partition round its central axis, which is the most usual form of the machine in practice. On a small scale, it may be constructed by wrapping one or more flexible lead pipes round a solid cylinder of wood, which forms a useful machine for raising water to small heights. It was formerly much used, but owing to its liability t become choked by mud, weeds, and other impediments, and the great difficulty of cleaning it out, it is seldom met with. It has, from its specious appearance of seeming to throw the entire weight of water that it is raising upon its axles, and the little friction with which these may be made to move by frictionrollers, had astonishing powers ascribed to it; but, if investicated, it will be found that the water is merely made to flow up an inclined plane; and whether water or any other weight be drawn up a five ! inclined plane, or it be stationary until moved by an inclined plane be.ng for ed under 1, as is the case with the

quantities of water contained in the several bends v, u, w, x, &c., the mechanical effort will be the same; consequently, this machine possesses no other mechanical advantage over other constructions of pumps, except that its motions are attended by less friction than belongs to most of

them.

The rope-pump of Vera, described in most books on hydraulics, consists of an upper and lower pulley, formed in the ordinary manner, but with several grooves in each, in which endless ropes of very loosely spun horse-hair or wool are made to move with great rapidity by a multiplying wheel connected with the upper pulley. The lower pulley, together with a great part of the rope, moves in the water, which is merely brought up by adhering to the ropes, and the rapidity of their motion. This, therefore, is but a very imperfect and rude kind of bucketpump, and is by no means deserving the place it has so long held in the catalogue of hydraulic machines.

Sarjeant's pump may be considered as a cheap and useful prime mover. It was originally applied to the raising of water at Irton Hall; and a small stream in the neighbourhood was brought by a wooden trough, into which was inserted a piece of two-inch leaden pipe, a part of which is seen at A, plate 4, fig. 6.

The stream of the pipe is so directed as to run into the bucket B, when the bucket is elevated; but so soon as it begins to descend, the stream flows over it, and goes to supply the wooden trough, or well, in which the foot of the forcingpump C stands, of three inches bore.

D is an iron cylinder, attached to the pumprod, which passes through it. It is filled with lead, and weighs about 240 lbs. This is the power which works the pump, and forces the water through 420 feet of inch pipe, from the pump up to the house.

At E is fixed a cord, which, when the bucket comes to within four or five inches of its lowest projection, becomes stretched, and opens a valve in the bottom of it, through which the water empties itself.

There is another machine for the purpose of procuring motion and power by water, which was invented by Dr. Barker towards the close of the last century, and which is generally known by the name of Barker's Centrifugal Mill. Its general construction is shown at fig. 7, plate IV., in which vu is a metal pipe of considerable height, its top v being widened or extended into a funnel shape. The pipe is maintained in its vertical position, as shown in the figure, by resting on a pointed steel pivot turning into a brass box w at the lower extremity, while the upper part has a cylindrical steel axis passing through the top yy of a frame which supports it: the pipe vu is consequently free to move round upon its own axis, which it does with very little friction. Towards the lower extremity of the pipe v u, and at right angles to its axis, two or more smaller pipes or arms with closed external ends are inserted as at z a, and an adjustable orifice is made at the side of each of these small pipes as near as possible to its end, and placed on opposite sides of such pipes,

so that water issuing from them may spout horizontally and in opposite directions, as shown at the letters and a. One end of a pipe B communicates with a supply of water which it delivers into the funnel head v without touching it in any part, and the supply of this pipe must be so regulated by a cock or otherwise, that it may constantly keep the pipe u v filled with water without running over, at the same time that the discharge is going on from the orifices za, which will deliver their water with a force proportionate to the perpendicular height of the column of water contained in u v; and, since the holes z a are in opposite directions, the water in passing from them will meet with such a resistance from the surrounding air as to throw the pipe u v, with its arms and axis x, into rapid roratory motion, and this axis may communicate its motion and power to wheel-work or machinery, or even to a mill-stone connected with its upper end. This machine is described and highly spoken of in almost all the books that teach of hydraulic machinery, but it does not appear to have been carried into practical effect in England.

The centrifugal pump may be considered as bearing some resemblance to Barker's Mill inverted, as the water in this case rises up the tube A A fig. 8, plate IV., from the reservoir E, and is thrown off by the centrifugal force at the ends of the lateral branch B C. This branch is furnished with valves at the extremities; and, a quantity of water having been poured into the lower vessel E, the cylinder and the lateral branch are also filled with water. The apparatus is then put into motion by turning the handle at G, and the centrifugal force driving out the valves at the extremities of the branch, the water rushes rapidly into the trough D, from which it returns into the reservoir through a hole at f. The water at the same time rises through a valve, at the bottom of the tube A A, opening upwards.

The Water Ram, or Bélier Hydraulique, as it was called by its inventor, M. Montgolfier, of Paris, is a highly useful and simple machine, for the purpose of raising water without the expenditure or aid of any other force than that which is produced by the momentum or moving force of a part of the water that is to be raised; and is one of the most simple and truly philosophical machines that hydraulics can boast. The action of this machine depends entirely upon the momentum that is generated whenever a body is put into motion, and its effect is so great as to give the apparatus the appearance of acting in defiance of the established laws of hydrostatic equilibrium; for a moving column of water of small height is made to overcome and move another column much higher than itself.

The form and construction of the water-ram

is shown at fig. 9. Suppose o to represent a cistern or reservoir, or the source of a spring which is constantly overflowing and running to waste, by means of a channel a few feet lower than itself, as at the level line p p. Instead of permitting the water to run over the sides of o, let it be conducted to the level line pp, by means of iron or other pipes q q connected with the side of the reservoir, and terminating by an

orifice 7', in which a conical or other valve s is placed so as to be capable of effectually closing the pipe when such valve is drawn upwards; is an adjustable weight fixed on to the spindle of the valves, by means of which the valve is kept down and open; any water therefore that is in the cistern o will flow down the pipe qq, and escape at the oritice 7, so long as the valve remains down, but, the instant it is raised and shut, all motion of the water is suspended, Thus situated, the adjustment of the weight t must take place, and, by adding to or subtracting from it, it must be made just so heavy as to be capable of sinking or forcing its way down wards, against the upward pressure of the water, the force of which will depend upon the perpendicular distance from the surface of the water in o, to its point of discharge at r (represented by the dotted line or). But the water by moving acquires momentum and new force, and consequently is no longer equal to the column o, to which the valve has been adjusted, but is superior to it, by which it is enabled to overpower the resistance of the weight 1, and it carries the valve up with it, and closes the orifice r. This is no sooner done than the water is constrained to become stationary again, by which the momentum is lost, and the valve and weight once more become superior, and fall, thus reopening the orifice and permitting the water to nove again; and, as the pressure of the water and the weight of the valve each become alternately superior, the valve is kept in a constant state of vibration, or of opening and shutting without any external aid, whatever. Such is the principle upon which the motion of the water in the pipe qq is produced; but the momentum generated cannot be instantly annihilated; and it is not only of sufficient power to raise the valve s, but likewise to burst open the lower end of the pipe qq, unless a sufficient vent be provided by which this accumulated force can escape. Accordingly a second valve u is placed near the lower end of the pipe q q, and is made to open upwards into an air-vessel, having a discharging pipe ; and consequently, whenever the valve s is closed, the water, which otherwise would have flowed from the orifice r, now opens the vaive u and enters the air-vessel, until the spring of the contained air overcomes the gradually decreasing force of the momentum, when the valve a closes, and that at s opens to permit the water to make a second blow or pulsation, and in this way the action of the machine continues unceasingly without any external aid so long as it is supplied with water, and remains in repair. A small running stream is necessary for this machine, as the water at o should be kept at one constant elevation to ensure the perfection of its action. A much greater quantity of water likewise escapes at the orifice r, between the pulsations, than can be raised in the delivering pipe, particularly if it extends to any considerable height; for the comparative quantity of water discharged through r, and permitted to run to waste at 7, must always depend upon the respective perpendicular heights of the pressing column o, and the delivered or resisting column ur, and the rapidity of the pulsations will like

wise depend on the same circumstances. A very insignificant pressing column ov is capable of raising a very high ascending column a 1, so that a sufficient fall of water may be obtained in almost every running brook, by damming up its upper end to produce the reservoir o, and carrying the pipes q q down the natural channel of the stream until a sufficient fall be obtained; for a considerable length of descending pipes from o tor is necessary to insure the certain effect of the machine, since, if the column 99 is not of sufficient length, its water will be thrown back into the reservoir, instead of entering the air-vessel, which requires to be replenished with air, and this is admitted into it by the self-acting shifting valve, shown at in the shaded part of it, which is an enlarged view of the air-vessel in an improved form; its valve is made by a ball at a, having a metal bridle over it to prevent its rising too high.

In taking the height to which water is to be raised by a pump, perpendicular height alone is to be regarded, and not lateral extersion, because fluids press according to their perpendicular height. Thus, if a pipe 100 feet lon. is six feet higher at one end than at the other, the six feet only are to be regarded as the height to which the water must be raised, and the 100 feet may be disregarded, except so far as it produces friction detrimental to the motion of the water. The height of a lift of water must be taken from the surface of the water which is to be liited to the surface of the cistern, or reservoir, or end of the pipe that is to receive or deliver it, and not from the bottom of the suction-pipe, because that pipe may descend any distance below the surface of the water to be raised without affecting the measurement, since the water will always rise to its own level within that pipe, without the aid of any exertion of force by the pump. Be careful, likewise, to introduce no right-angled or short turns into pipes, if they can be avoided; but let every such turn be a regular curved sweep, and the larger and more regular that sweep is made, the less impediment it will offer to the passage of the water.

In order to determine the force or power necessary to work a pump of any description, the height to which the water is to be raised must always be taken into account; for this height multiplied into the area of the piston, and reducel to any of the usual denominations of weight, will give the amount of resistance to be overcome (friction of the pump only excepted). The size of the pipe containing the water is quite immaterial, provided it be large enough to prevent friction and unnatural velocity in the water; and the entire perpendicular height from the surface of the water raised to the point where it is delivered, whether occupied by suction or feeding-pipe, or delivering pipe from a forcing pump must be added together, and considered as the height of the lift: so that if a lift and force-pump of four inches in diameter, in the working-barrel, has ten feet of three-inch suction-pipe below its piston, and twenty feet of two-inch delivering-pipe (including the length of the working-barrel) above it, the column to be lifted will be equal to thirty feet of four-inch

pipe filled with water. The contents in gallons of thirty feet of four-inch pipe must therefore be found, and, as each imperial gallon of water weighs 10 lbs. avoirdupois, the weight or load upon the pump will be immediately found, to which must be added from one-tenth to onesixth, according to the construction of the pump, for friction. The load upon an eccentric or any other pump may be found by the same rule, if the effective horizontal area of the piston, or its substitute, be found; and this be in like manner multiplied into the height of the lift. It therefore becomes important to know the weight and quantity of water which a certain length of pipe of any given diameter will contain, and a tolerably close approximation to this may be obtained by squaring the diameter of any pipe in inches, and cutting off the last figure of the product by a decimal point, which will nearly give the contents in ale-gallons of one yard in length of such pipe. Thus, for example, if a pipe is six inches in diameter, 6 times 6 make 36, and introducing the decimal point would reduce this number to 3:6, so that one yard of such pipe would contain three gallons and sixtenths. If a three-inch pipe had been taken, then 3 x 39; consequently there remains but one figure to cut off. The gallons' place must therefore be supplied by a cypher, thus, 09, and the yard of such pipe would contain but nine-tenths of a gallon.

For greater certainty, however, the following table and rules are introduced. They are extracted from Brunton's Compendium of Mechanics; a recent little work, published at Glasgow, and which is replete with useful information :TABLE of the Contents of a Pipe one inch diameter for any required Height.

standard for pipes of any other size, by observing the following

Rule.-Multiply the numbers found in the table against any height by the square of the diameter of the pipe, and the product will be the number of cubic inches, avoirdupois ounces, and wine gallons of water, that the given pipe will contain.

Example. How many wine gallons of water are contained in a pipe six inches diameter, and sixty feet long :-

2-4480 × 3688′1280 wine gallons.

The wine gallon contains 231 cubic inches, and the new imperial gallon 277-274 cubic inches; therefore, to reduce the wine to the imreduction of the ale gallon, which contains 282 perial gallon, divide by 1.20032; and for a like cubic inches, divide by 0.98324.

HYDROSULPHURETS.

Compounds of

sulphureted hydrogen with the salifiable bases. HYDROTHIONIC ACID. Sulphureted hydrogen, the hydrosulphuric acid of M. Gay dwp. Purger of water or phlegm. Fr. bydrotique; Gr.

Lussac.

HYDROTIC, n. s.

into hydroticks and purgers of bile. He seems to have been the first who divided purges Arbuthnot.

HYDRUNTUM, in ancient geography, a noble and commodious port of Calabria, from which there was a short passage to Apollonia. (Pliny) famous for its antiquity, and for the fidelity and bravery of its inhabitants; now called Otranto. Long. 19° 15′ E, lat. 40° 12′ N.

HYEMANTES, in the primitive church, offenders who were not allowed to enter the porch of the churches with other penitents, but were obliged to stand without, exposed to the inclemency of the weather, even in winter..

HYEN, n. s. ? Fr. hyene; Lat. hyana. An HYE'NA, n. s. Sanimal like a wolf; said fabulously to imitate human voices.

I will weep when you are disposed to be merry; I will laugh like a hyen, when you are inclined to sleep. Shakspeare.

Out, out, hyena; these are thy wonted arts, And arts of every woman false like thee.

Milton. Samson Agonistes. The hyena was indeed well joined with the beaver, as having also a bag in those parts, if thereby we understand the hyena odorata, or civet cat.

Browne's Vulgar Errours.
Oh the bewitching tongues of faithless men!
'Tis thus the false hyena makes her moan
To draw the pitying traveller to her den.

A wonder more amazing would we find;
The hyena shews it of a double kind;
Varying the sexes in alternate years,
In one begets, and in another bears.

Otway.

Dryden's Fables. Thomson. The keen hyena, fellest of the fell. Tearing, and grinning, howling, screeching, swear

ing,

And with hyena laughter, died despairing.

Byron. Don Juan. HYGEIA, or HYGIEA, Greek, 'Yyıɛta, in mythology, the daughter of Esculapius, and the goddess of health, among the ancient Greeks, called by the Romans Salus. See SALUS.

HYGINUS (Caius Julius), a grammarian, the freedman of Augustus, and the friend of Ovid,