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of girders and beams of cast iron. (See article, Bramah's hydrostatic press.) Its latest and perhaps most remarkable duty is that of lifting the iron-work of tubular bridges en masse from the water level to their final altitude.

Hydrostatic presses consist essentially of two distinct parts, viz. the press, or machine in which the force acquired is applied, and the pumping apparatus, by which the water is forced into the press; these two parts of the entire machine being connected only by the pipe Fig. 2.

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show the main parts of the press, viz. the cylinder, into which the water is admitted; the ram, or solid plunger or piston; and the crosshead by which the pressure at the end of the ram is distributed over a lengthened surface for use. The figures show the cylinder as supported in a frame upon girders, in a manner similar to that adopted in raising the tubes of the railway bridge recently erected at Conway.

Fig. 3 shows the section of a portable forcing-pump as commonly used for proving castings with the hydraulic press, for which purpose the press is applied horizontally, and mounted on an iron carriage for portability. But, however varied in arrangement for particular purposes, the pump and the press consist of the same essential parts, as follows: the pump comprises a cistern or kind of pail, for containing the water, and into which a barrel descends nearly to the bottom. The barrel is fitted with a plunger, by working which, the water is driven through a small tube or pipe into the press. The pump is furnished with a safetyvalve, and also with a screw for letting off the water as required. The press consists of a strong hollow cylinder of cast iron, close at one end, and of a solid ram working through the other end, the water-pipe being inserted through the metal of the cylinder in a watertight screwed aperture. Fig. 1 is an elevation of the press; fig. 2, a vertical section of the press, taken at right angles to the elevation; and fig. 3, a vertical section of a pump: a is the cast-iron cylinder; b, the ram; c, the casing or frame of the cylinder; d d are two castiron girders supporting the casing; e is the cast-iron cross-head; ff, two guide-rods; g, the water-pipe from the pump, with a lever-valve at h, by closing which the pressure will be retained, should the pipe burst. On fig. 3, j shows the other

t, a tube depending from the valveseats, and screwed upon it: this tube reaches nearly to the bottom of the cistern, and is perforated at the end with minute apertures, through which the water is admitted without dirt or particles, which would injure the working of the pump; u is the plunger, which works through a stuffing-box on the top of the barrel, and is made with a slot at v, to receive the link op, which is pinned to it and also to the pump handle; w is the plunger-rod, screwed into the upper end of the plunger; y, the pumphandle, jointed to the standard at x. During the first part of the action of the pump, while no great pressure is yet produced, the handle is

pinned to the outer of these holes, as it makes a larger stroke with the piston, and thus saves time: the pin is afterwards removed to the

inner hole, to have all the advantage of the leverage. z is the upper or discharge valve, with a conical end: it is introduced from the top, and covered with a short screw, which likewise regulates the lift of the valve. This valve is formed by being simply filed flat out of the round.

The rule for finding the increase of power commanded by the pump is derived,-first, from the ratio of the areas of cross section of plunger of pump and ram of press; and, secondly, from the ratio of the leverage of the pump-handle. Thus suppose the plunger to be inch and the ram 6 inches in diameter, and the arms of the lever or handle as 1 to 4, the power will be thus found: •52 : 62 multiplied by 1 : 4

that is, 1 576. :

25: 144,

And thus a power equal to 20 fbs., applied on the end of the pumphandle, will produce a pressure

equal to 11,520 lbs. on the ram, or 5 tons 2 cwt. 3 qrs. 12 fbs.

Each of the presses applied at Conway was worked by a steam engine having a horizontal cylinder 17 inches in diameter and 16 inches stroke, with piston-rods working through stuffing-boxes at both ends of the cylinder. The piston-rods worked two forcing-pumps, with plungers 1 inch diameter and 16 inches stroke. The rams of these presses were each 5 feet 2 inches long and 18 inches in diameter, with a space nearly inch wide around. The cylinders were 37 inches diameter externally, and 20 inches internally, the metal being 8 inches in thickness: the orifice of the water-tubes & inch in diameter. Hydrostatic paradox. This may be explained upon the same principles as the mechanical powers; and an explanation conducted in this manner strips it of its paradoxical appearance.

Hydrostatics, the science which treats

of the mechanical properties of fluids; strictly speaking, the weight and equilibrium of fluids. The weight and equilibrium of fluids at rest are the objects of this science. When the equilibrium is destroyed, motion ensues; and the science which considers the laws of fluids in motion is hydraulics. Hygrometer: this instrument is used to ascertain the quantity of moisture held in the atmosphere. There are several kinds of hygrometers in use, namely, De Luc's, Saussure's, Leslie's, and Professor Daniell's. The latter is considered preferable.

ICE

ICE-HOUSE, a subterranean chamber for preserving ice free from mixing with the ordinary changes of temperature

Ich Dien, in heraldry, 'I serve' Ichnography, in drawing. The ichno

graphy of a building represents the plan or ground-work; the ortho

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Hypothral, open above: in temples of this description the cella was in part exposed to the air: they had a double range of columns within the cella, dividing it into three alæ, or aisles. The alæ on either side were roofed, but that in the middle had no covering. Hypætrum, a latticed window over the entrance-door of a temple Hyperbola, a section of a cone made by a plane, so that the axis of the section inclines to the opposing leg of the cone, which in the parabola is parallel to it, and in the ellipse intersects it Hyperthyrum, that part of the frame of a doorway which is over the supercilium } Hyperthyrum, in Greek architecture, a frieze and cornice supported by friezes and consoles Hypocastanum, or chestnut brown, is a brown lake prepared from the horse-chestnut: it is transparent and rich in colour, warmer than brown pink, and very durable both in water and oil: in the latter it dries moderately well Hypocausis, among the Greeks, a furnace with flues running underneath the pavement of an apartment, to increase the temperature Hypocaustum, the stove-room of a bath, in which was placed the præfurnium for heating the caldaria Hypogeum, in ancient architecture, a name common to all the underground parts of a building Hypotrachelium, that part of the capital of a column which occurs between the shaft and the annulets of the cchinus

IMP

graphy the front; and the scenography the whole building. Icosahedron, in geometry, a regular body or solid, consisting of twenty triangular pyramids

Image, a term applied to a statue Imbowment, an arch or vault Impages, the horizontal parts of the

frame-work of doors, commonly termed rails

Impale, in heraldry, to conjoin two coats or arms, as a wife's with those of her husband Impetus, in mechanics, violent tendency to any point, violent effort, force, momentum, motion Impinge, in mechanics, to fall against, to strike against, to clash with Impluvium, the cistern in the central

part of the court or atrium of a Roman house, to receive the rainwater

:

Impost, the horizontal mouldings or capitals on the top of a pilaster, pillar, or pier, from which an arch springs in classical architecture the form varies in the several orders. Sometimes the entablature of the order serves for the impost of an arch. Impost,archivolt, and key-stone. The height of the impost should be from one-ninth to one-seventh of the width of the aperture, and the breadth of the archivolt not more than an eighth nor less than a tenth of it. The breadth of the under side of the key-stone should be the same as the breadth of the archivolt, and its sides, of course, concentric; its length, once and a half its breadth, but not more than double its breadth.

Impulsive force is that which acts during an extremely short time, and is so called because the forces that take place in any impulse, or impact, are speedily exhausted Incise, to cut; to engrave; to carve Inclined plane (the), in mechanics, is a plane which makes with the horizontal plane any angle whatever, forming one of the simplest mechanical powers. The inclination of the plane is measured by the angle formed by two lines drawn from the sloping and the horizontal plane, perpendicular to their common intersection.

Increment, an increase; produce Incrustation. If water, impregnated with calcareous matter, remains

long in contact with extraneous substances, an earthy incrustation takes place that soon encloses the encrusted substance, which is then said to be petrified.

Indian Architecture consists of two distinct styles, the Buddhist and the Brahminical,—the former being the earliest, and consisting of topes or tumuli, large domical buildings of brick or stone, either quite solid or containing one or more small chambers, in which are deposited relics, coins, and other similar objects, which the greater number of them were erected to enshrine.

The principal topes are now found in Ceylon and Affghanistan, but they also exist in Burmah and in other neighbouring countries.

The next class of Buddhist buildings are the Chaitya halls, similar in plan and use to the early basilica: these exist principally in caves in India. And lastly, viharas or monasteries, in which the monks attached to the Chaitya halls resided: these also exist principally as caves in India, and as structural buildings in all countries where Buddhism is still practised.

Brahminical or Hindoo architecture consists mostly of temples, properly so called. These in almost every instance are towers, square in plan, or nearly so, built over the cell or sanctum of the temple. In the south of India, the upper part forms a right-lined pyramid; in the north, the outline is curvilinear, sometimes tapering to a spire.

To these towers are attached porches of greater or less dimensions. In the north there are generally square halls without pillars in the south, as universally pillared sometimes attached, at others detached from the temple itself in the latter case, in the south, some of the porches possess from 500 to 1000 pillars, though this is never the case in the north.

These temples are generally surrounded by a square court: in the

south, three, four, and sometimes even seven such enclosures surround the principal cell, the outer one being, in many instances, some miles in circumference.

These Hindoo temples exist sometimes, though rarely, as rockcut temples; but generally they are structural.

Between these styles comes a third, the Jaina style, being a mixture of the two, possessing some of the characteristics of both, and frequently displaying more elegance than the first, and less tawdriness than the other. By the introduction of domes, whose use was thus brought to great perfection, an element was added which was a great improvement on the other two styles, and from which that of Jaina originated.

The absence of the arch in all constructions of every age is general throughout India, as the principle was quite unknown.

The upper parts of the buildings were supported on square piers or pillars, and from all sides of their capitals brackets projected equal to their width, and leaving generally a space equal to three diameters between their greatest projec-. tion, thus leaving only one-half of the whole length of the architrave unsupported; but when a greater space was required, a succession of projecting brackets, placed above each other, was adopted, sometimes meeting in the centre, and thus having the effect of the horizontal arch.

Indian Ink: the pigment well known

under this name is principally brought from China in oblong cakes, of a musky scent, prepared for painting in water, &c. Indian red, a colour, is brought from Bengal, and is a very rich iron ore, or peroxide of iron. It is an anomalous red, of a purple-russet hue, of a good body, and valued, when fine, for the pureness and lakey tone of its tints

INN

Indian yellow is a pigment long employed in India and subsequently introduced generally into painting in European countries. It is imported in the form of balls, is of a fetid odour, and is produced from the urine of the camel. It has also been ascribed, in like manner, to the buffalo, or Indian cow, after feeding on mangoes; but the latter statement is incorrect. Indian yellow resists the sun's rays with singular power in water-painting. Indicator, the apparatus for showing the force of the steam, and the state of exhaustion in the cylinder during the stroke

Indigo, or Indian blue, is a pigment manufactured in the East and West Indies from several plants, but principally from the anil or indigofera Inertia, the passiveness of matter: matter has not the power of putting itself into motion, neither has it the power of stopping itself when put into motion by the action of an external force, as it requires as much force to stop a body as it requires to put it in motion Inflammable air, hydrogen gas Influx, in hydraulics, the act of flowing into any thing, as the tide into a bay or river

Injection-cock, the stop-cock in the

ejection-pipe, for shutting off the supply of cold water used for the condensation of steam Injection-pipe, the pipe through which the injection water passes to the condenser; in a steam vessel the injection-pipe is open to the sea, at the bottom of the vessel Inn or Hostel, anciently a lodginghouse, or a house of lodging and refreshment for travellers: houses for lodging the collegians at Cambridge and Oxford were so called Inns of court, houses in which there are many lodgings for the accom

modation of students and practitioners at law

Innate force, in physics, the vis inertia Inner-post, in ship-building, a piece

brought in at the fore-side of the