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rsmnumicates with F, but acts through G upon the lower part of the piston. H, and raises it; while the contents of the great cylinder above that piston are driven out through F, and pass throngh the opening at D into R. It may be observed, that the column which acts against the piston is assisted by the pressure of the atmosphere, rendered active by the column of water hanging in R, to which that assisting pressure is equivalent, as has already been noticed. When the piston has ascended through a certain length, another slide or block upon the pit-rod (not seen) applies against the tail, K, of the tumbler, which it raises and again overseas, producing once more the position of the plugs, D E, here delineated, and the consequent descent of the great piston, H, as before described. The descent produced the former effect on the tumbler and plugs, and in this manner it is evident that the alternations will go on without limit, or until the manager shall think fit to place the tumbler and plugs, D E, in the positions of rest, namely, so as to stop the passages, F and G. The length of the stroke may be varied by altering the positions of the pieces, I, and the other lower down, which will shorten the stroke, the nearer they are together; as in that case they will sooner alternate upon the tail, K. As the sudden stoppage of the descent of the column, A B, at the instant when the two plugs were both in the waterway might jar and shake the apparatus, those plugs are made half an inch shorter than the depth of the side holes, so that in that case the water can escape directly through both the small cylinders to R. This gives a moment of time for the generation of the contrary motion in the piston, and the water in G G G, and greatly deadens the concussion which might else be produced. See Steam Engine.
Some former attempts to make pressure engines upon the principle of the steam-engine have failed; because water not being elastic, could not be made to carry the piston onwards a little, so as completely to shut one set of valves and open another; in the present judicious construction the tumbler performs the office of the expansive force of steam at the end of the stroke.
Engine/of driving piles, used at building Westminster bridge, is constructed as follows: A, (Plate V. Miscel. fig. 3.) is the great shaft, on which are the great wheel and drum: H, the great wheel with cogs, that turns a trundle head with a fly, to prevent
the horse's falling when the ram is discharged; C, the drum on which the great rope is wound ; D, the follower (with a roller at one corner) in which are contained the tongs, to take hold of the ram, and are fastened to the other end of the great rope, which passes over the pulley, near the upper end of the guides between which the ram falls; E, the inclined planes, which serve to open the tongs, and discharge the ram; F, the spiral barrel that is fixed to the drum, on which is wound a rope with a counterpoise, to hinder the follower from accelerating, when it falls down to take up the ram; G, the great bolt which locks the drum to the great wheel; H, the small lever, which has a weight fixed at one end, passes through the great shaft below the great wheel, and always tends to push the great bolt upwards, and lock the drum to the great wheel; I, the forcing bar, which passes through the hollow axis of the great shaft, bears upon the small lever, and has near the upper end a catch by which the crooked lever keeps it down; K, the great lever, which presses down the forcing bar, and discharges the great bolt at the time the long end is lifted up by the follower; L, the crooked lever, one end of which has a roller, that is pressed upon by the great rope, the other end bears upon the catch of the forcing bar during the time the follower is descending; M, the spring that presses against the crooked lever, and discharges it from the catch of the forcing bar as soon as the great rope slackens and gives liberty to the small lever to push up the bolt.
By the horse's going round, the great rope is wound about the drum, and the ram is drawn up, till the tongs come between the inclined planes, where they are opened, and the ram is discharged.
Immediately after the ram is discharged, the roller, which is at one end of the follower, takes hold of the rope that is fastened to the long end of the great lever, and litis it up; the other end presses down the forcing bar, unlocks the drum, and the follower comes down by its own weight
As soon as the follower touches the ram, the great rope slackens, and the spring, M, discharges the crooked lever from the catch of the forcing bar, and gives liberty to the small lever to push up the great bolt, and to lock the drum to the great wheel, and the ram is drawn up again as before.
ENGINEER, in the military art, an able, expert man, who by a perfect knowledge in mathematics, deliueatcs upon paper, or marks upon the ground, all sorts of forts, and other works proper for offence and defence. He should understand the art of fortification, so as to be able, not only to discover the defects of a place, but to find a remedy proper for them, as also how to make an attack upon, as well as to defend the place. Engineers are extremely necessary for these purposes: wherefore it is requisite that, besides being ingenious, they should be brave in proportion. When at a siege the engineers have narrowly surveyed the place, they are to make their report to the general, by acquainting him which part they judge the weakest, and where approaches may be made with most success. Their business is also to delineate the lines of circmnvallation and contravalIation, taking all the advantages of the ground; to mark out the trenches, places of arms, batteries, and lodgments, taking care that none of their works be flanked or discovered from the place. After making a faithful report to the general of what is a doing, the engineers are to demand a sufficient number of workmen and utensils, and whatever else is necessary.
ENGRAFTING, or Grafting, in gardening. See the article Grafting.
ENGRAILED, or Ingrailed, in heraldry, a term derived from the French, bail; and signifying a thing the hail has fallen upon and broke off the edges, leaving them ragged, or with half rounds, or semicircles, struck out of their edges.
ENGRAVING. This term is at present confined to the art of excavating copper and wood, in lines, in so judicious a manner as to produce imitations of paintings and drawings when printed on paper. It is certain that engraving for the production of prints was unknown long after the practice of painting in oil had arrived to great perfection, but good prints are common from plates engraved in the fifteenth century, many of which are landscapes most laboriously, and even excellently performed by the graver, although it is well known that the instrument just mentioned cannot freely express those serrated and serpentine lines necessary for foliage and Short grass intermixed with plants, since so admirably delineated in etchings. A goldsmith of Florence, named Maso Finiguerra, is said to have discovered the art; but this assertion must undoubtedly merely apply to his obtaining impressions from lines engraved originally without the least idea of such a result; were we to examine the subject
closely, it might be proved, that onUmcs have been cut in metals, representing figures, Sec from the most remote periods of antiquity, but being subject to decay, they have not reached our time as the more durable granites have done, embellished with hieroglyphics cut in them in a manner which might be printed on paper. Arguing from these premises, it may be inferred, that the antients understood the art of engraving in metal, though without conceiving that the copies of their productions might be multiplied by means of ink on soft white cloth, or similar materials. Albert Durer, born in 1470, and who died at Nuremberg 1528, is said to have been the first person on record claiming the name of an engraver in the long list of celebrated artists; but certainly very excellent engraved brass figures, the lines filled with substances to show them more clearly, are now extant on tombs in some hundreds of churches in England, the dates of many of which are prior to the time of his birth. This fact will serve to prove that the printing of engraved plates was discovered between 1470 and 1528; indeed the perfection that engraving had reached in the latter century, plainly demonstrates that the use of the graver was by no means a modern discovery. The encouragement of the fine arts has ever been a distinguishing trait of the inhabitants of the continent of Europe; it is not wonderful, therefore, that engraving closely followed the footsteps of the parent arts, and flourished there in greater perfection than in England, where they have been in a state of miserable depression till within the last century, when literature was supposed to receive some aid from the graver, the booksellers taking the hint, have encouraged the predilection'of the public, which has operated as a stimulus to the artist, and the consequence is, that the graphic embellishments of British topographical and poetical works are equal, if not superior, to any in Europe.
Historical engravings for the port folio and furniture seemed at one period to advance rapidly towards perfection, to which the late Alderman Boydell greatly contributed; but the death of Strange, Hall, and Woollet, have been almost fatal to the hopes of the amateur, which rest, in a great measure, upon Heath, Sharp, Bromley, and a few others, as in this particular instance we do not include those eminent foreigners who have, or do at present reside in England. Whatever deficiencies we may discover in the prosecution of the arts in this country, is fortunately not to be attributed to want of genius, or relaxation from study in the artist; the chill of apathy in the rich, who view a wretched coloured aquatint with the same or more pleasure than the most laboured production of the graver, is the baleful cause of the languishing state of historical engraving. When persons capable of affording patronage are taught discrimination, future Woollets will fascinate the best judges of engraving.
We shall now proceed to explain the methods of executing different descriptions of engraving. The graver, an instrument of steel, is the primary object for engraving on copper; it is square for cutting of broad lines, an d lozenge for the finest, and must be tempered to that exact state which will prevent the point from breaking or wearing by its action on the metal; to obtain this State, it is customary to heat it when too hard on the end of a red hot poker, till it assumes a straw colour, and then cool it in oil; if held too long, it will become blue, Soft, and useless, till the process of tempering the steel is renewed. As it is possible a graver may be of the proper degree of solidity, except in some inconsiderable part, it would be well to rub it on the oil stone till that is ascertained. The graver is inserted in a handle of hard wood, resembling a pear with a longitudinal slice cut off, which is to enable the artist to use it as flat on the plate as his fingers and thumb will permit. In order to prepare this instrument for cutting a clear smooth line, great care must be taken in sharpening it, that the original general form should be pre. served, by laying the sides flat upon the oilstone, and rubbing them so as not to round them in the least, after which the graver is to be held sloping towards the person, and rubbed thus till the point is extremely sharp, besides these .precautions, it will be necessary that the point should not be exactly in a right line with the lower part of the graver, but a little higher, that it may not press too deep into the copper. In rubbing the sides of the graver, the usual manner has been to confine the right arm close to the side, placing the fore finger of the left hand on the upper side of the tool when on the stone. This instrument is used for finishing the imperfections discoverable in etchings, and exclusively in engraving writing.
The scraper is a long triangular piece of steel, tapering gradually from the handle to the point; the three edges produced by this
form, being sharpened on the oilstone, are used for scraping off the roughness occasioned by the graver, and erasing erroneous lines.
The burnisher is a third instrument of steel, hard, round, and highly polished, for rubbing out punctures or scratches in the copper. The oil-stone has been already mentioned, to those may be added the needle or dry point for etching, and making those extremely fine lines which cannot be done with the graver.
Cushions made of soft leather, and filled with fine sand, hence called sand-bags, are required for the support of the plate in engraving, which, from their circular surface, permits the copper to turn with ease, and facilitates the cutting of those true curves composing the shading of most subjects. The oil rubber and charcoal are necessary for polishing the plate.
Every thing depends upon the free use of the grayer, therefore the utmost care must be taken to hold it properly, by preventing the interposition of the fingers between the graver and the plate, with the fore finger on the upper angle, which enables the artist to conduct it parallel with the substance engraved, thus preventing the point from entering deeply, and impeding the progress of the tool.
To engrave well requires good materials, though those are nearly confined to two, the graver, and the best copper, the latter should be free from flaws, small punctures, well hammered to close the pores, and polished to such a degree as to be free from the slightest scratches.
To trace the design intended for engraving accurately on the plate, it is usual to heat the latter sufficiently to melt white wax, with which it must be covered equally and thin, and suffered to cool; the drawing is then copied in outlines with the black-lead pencil on paper, which is laid with the pencilled side upon the wax, and the back rubbed gently with the burnisher, which will transfer the lead to the wax. The design must next be traced with an etching needle through the wax on the copper, when, on wiping it clean, it will exhibit all the outlines ready for the graver.
The table intended for engraving on should be perfectly steady, and the sandbags placed equally firm; in cutting of curved or undulating lines, the graver must be held still, or moved, to suit the turning of the plate with the left hand, but when straight lines are intended, the plate is to be held stationary, and the graver urged forward with more or less pressure, according to the thickness of the line. Great care is necessary to carry the hand with such steadiness and skill as to prevent the end of the line from being stronger and deeper than the commencement; and sufficient space must be left between the lines to enable the artist to make those stronger, gradually, which require it. The roughness or burr occasioned by the graver must be removed by the scraper, the lines filled by the oil-rubber, and the surface of the copper cleansed, in order that the progress of the work may be ascertained.
If any accident should occur by the slipping of the graver beyond the boundary required, or lines are found to be placed erroneously, they are to be effaced by the burnisher, which leaving deep indenting, those must be levelled by the scraper, rubbed with charcoal and water, and finally polished lightly with the burnisher.
As the uninterrupted light of the day causes a glare upon the surface of the copper, hurtful and dazzling to the eyes, it is customary to engrave beneath the shade of silk paper, stretched on a square frame, which is placed reclining towards the room near the sill of a window.
Such are the directions and means to be employed in engraving historical subjects; indeed the graver is equally necessary for the completion of imperfections in etching, to which must be added the use of the dry point in both, for making the faintest shades in the sky, architecture, drapery, water, &c &c.
Engrarlng of Mazotintoi differs entirely from the manner above described; this method of producing prints, which resemble drawings in Indian ink, is said by Evelyn, in his history of chalcography, to have been discovered by Prince Rupert, and was some years past a very favourite way of engraving portraits and historical subjects; of the former, the large beads by Fry are of superior excellence.
The tools required for this easy and rapid mode of proceeding, are the gronnding-tool, the scraper, and the burnisher; the copperplate should be prepared as if intended for the graver, and laid flat upon a table, with a piece of flannel spread under it to prevent the plate from slipping; the grounding-tool is then held perpendicularly on it, and rocked with moderate pressure backwards and forwards, till the teeth of the tool have equally and regularly marked the copper from side to side, the operation is after
wards repeated from end to end, and from each corner to the opposite; but it is necessary to observe, that the tool must never be permitted to cut twice in the same place; by this means the surface is converted into a i ongh chaos of intersections, which, if covered with ink and printed, would present a perfectly black impression upon the paper.
To transfer the design to be scraped, it is usual to rub the rough side of the plate with a rag dipped into the scrapings of black chalk, or to smoke it with burning wax taper, as in the process for etching; the back of the design is then covered with a mixture of powdered red chalk and flake white, and laid on the plate through which it is traced; particles of red, in the form of the outlines, are thus conveyed to the black chalk on the plate, which are to be secured there by the marks of a blunted point; the process must then be carried on with the scraper, by restoring the plate in the perfectly light parts of the intended print to a smooth surface, from which the gradations are preserved by scraping off more or less of the rough ground; but the burnisher is necessary to polish the extreme edges of drapery, 4c, where the free touch of the brush in painting represents a brilliant spot of light. The deepest shades are sometimes etched and corroded by aqua fortis, and so blended with the mezzotinto ground added afterwards, that there is nothing offensive to the eye in the combination.
Many proofs are required to ascertain whether the scraping approaches the desired effect, which is done by touching the deficient parts with white or black chalk, on one of the proofs from the original drawing, and then endeavouring to make the plate similar by further scraping, or re-laying the ground with a small tool made for this particular purpose, where too much of the roughness has been effaced.
Engraving on Steel is confined to the cutting of punches, for the conveyance of any form a certain depth into that or any other metal, seals, and dyes, for impressing the designs of coins, medals, Ste. on gold, silver, or copper, &c. The punches are engraved from models in wax made in relievo, and when completed, are tempered to that degree of solidity which will bear the violent blows without blunting the finest parts or breaking them, necessary to produce the matrix in the steel intended for striking of medals or coins, which must be heated to prevent such a disaster, and tempered again, for a similar reason to the preceding, niter it is finished.
There are several tools used in finishing of dyes, which are gravers, chissels, and flatters, and many little punches for making ornamental borders and mouldings to coins and medals; the latter are always in greater relief than the former, and consequently more difficult to execute in perfection.
Engraving on precious Stones is accomplished with the diamond or emery. The diamond possesses the peculiar property of resisting every body in nature, and, though the hardest of all stones, it may be cut by a part of itself, and polished by its own particles. In order to render this splendid substance fit to perform the operations of the tool, two rough diamonds are cemented fast to the ends of the same number of sticks, aud rubbed together till the form is obtained for which they arc intended ; the powder thus produced is preserved, and used for polishing them in a kind of mill furnished with a wheel of iron; the diamond is then secured in a brazen dish, and the dust mixed with olive oil applied, the wheel is set in motion, and the friction occasions the polished surface so necessary to give their bistre due effect. Other stones, as rubies, topazes, and sapphires, are cut into various angles on a wheel of copper, and the material for polishing those is tripoli diluted with water.
A leaden wheel, covered with emery mixed with water, is preferred for the cutting of emeralds, amethysts, hyacinths, agates, granites, &c. Ace and they are polished on a pewter wheel with tripoli; opal, lapis lazuli, &c. are polished on a wheel made of wood.
Contrary to the method used by persons who turn metals, in which the substance to be wrought is fixed in the lathe, turned by it, and the tool held to the substance, the engraver of chrystal, lapis lazuli, &c, fixes his tools in the lathe and holds the precious stone to them, thus forming vases, or any other shape, by interposing diamond dust mixed with oil, or emery and water, between the tool and the substance as often as it is dispersed by the rotary motion of the former.
The engraving of armorial bearings, single figures, devices, &c. on any of the above atoms after they are polished, is performed through the means of a small iron wheel, the ends of the axis of which are received within two pieces of iron, in a perpendicu
lar position, that may be closed, or otherwise, as the operation requires; the tools are fixed to one end of the axis and screwed firm, the stone to be engraved is then held to the tool, the wheel set in motion by the foot, and the figure gradually formed. The materials of which the tools are made is generally iron, and sometimes brass, they are flat, like chisels, gouges, ferules, and others have circular heads. After the work is finished the polishing is done with hair brushes, fixed on wheels, and tripoli.
JEngracMur on Wood has been practised for several centuries, and originally with tolerable success, it languished for great part of the 18th century, but revived towards the close, and is still practised in a manner which reflects credit on the ingenuity of the age. Bewick will long be remembered by his works in this style of engraving, and his imitators have been numerous and successful. As it is entirely different from engraving on copper, the artist already acquainted with that mode would find himself at a loss how to proceed on wood, as the lines, instead of being cut into the substance, are raised like the letters of printing types, and printed in the same manner.
The wood used for this purpose is box, which is preferred for the hardness and closeness of its texture; the surface must be planed smooth and the design drawn on it with a black-lead pencil, the graver is then used, the finer excavations from which are intended for white interstices between the black lines produced by leaving the box untouched, and the greatest lights are made by cutting away the wood entirely of the intended form, length, and breadth; but the deepest shades require no engraving. Much of the beauty of this kind of engraving depends upon the printing, nor is it every artist who can excel in it, as expedition and freedom are not to be attained; in short, the best wooden cuts are evidently the products rather of perseverance and ingenuity than easy confidence in ability, observable in every line of fine_ etchings. There are some who succeed to admiration in representing foliage and plants, but unfortunately a few months practice will enable a pupil to etch them on copper with greater truth : drapery and architecture may be well done in wood, but the faces and limbs of figures never look well.
Such are the different descriptions of engraving which do not require the aid of