into military and civil. The duties of the military engineer (since everything relating to the service of artillery is now confided to a particular corps) comprehend the construction of fortifications, both permanent and temporary, including the trenches and batteries required in sieges; also of barracks, magazines, and other works connected with war. In France, the title of engineer is given to those who are engaged in trigonometrical surveying and in the practice of naval architecture. Thus the French have a corps of ingénieurs géographes, of ingénieurs d'hydrographie, and of ingénieurs de marine.

Military engineering will not occupy our attention in this work; but the various important branches and ramifications of civil engineering will be considered under their respective heads. The profession of the civil engineer, as defined in the Charter of Incorporation of the Institution of Civil Engineers, London, is, "The art of directing the great sources of power in nature for the use and convenience of man, as the means of production and of traffic in states both for external and internal trade, as applied in the construction of roads, bridges, aqueducts, canals, river navigation, and docks, for internal intercourse and exchange; and in the construction of ports, harbours, moles, breakwaters, and lighthouses; and in the art of navigation by artificial power for the purposes of commerce; and in the construction and adaptation of machinery; and in the drainage of cities and towns." Civil engineering is both a science and an art as a science, it includes the general principles of mechanics and construction; shows how we may ascertain the strains to which a structure is exposed; the dimensions and proportions which should be given to its several parts, so as to be able to resist such strains without injury. As an art, civil engineering shows how scientific principles may be applied to the construction of works, and how used and modified so as to meet the difficulties which constantly arise in practice.

:

The civil engineer, being concerned in almost every kind of construction, ought to be a highly accomplished man of science; and, indeed, there are few men in any profession who can command so large an amount of scientific and practical knowledge as the civil engineer. The following classified arrangement' of the several branches of civil engineering, with their subdivisions, will not only serve to show the extent of the subject, but will guide the student in pursuing a systematic scheme in the attainment of his professional knowledge.

SYNOPSIS OF THE SCIENCE OF CIVIL ENGINEERING.

I. MENSURATION.

I. SURVEYING.-1. Description of instruments; their use and adjustment. 2. Surveying in general. 3. Trigonometrical surveying. 4. Hydrographical surveying. 5. Mining surveying.

II. LEVELLING.-1. Levelling instruments; their

(1) From Mr. Law's "Rudiments of Civil Engineering," pub

lished in Weale's Rudimentary Series. 1850.

use and adjustment. 2. Practice of levelling. 3. Measuring heights with the barometer.

III. DRAWING AND PLOTTING.-1. Instruments for drawing and plotting; their use. 2. Plotting surveys, and making plans. 3. Plotting levels and making sections. 4. Preparing parliamentary plans and sections. 5. Preparing working and contract plans and sections. 6. Preparing detail drawings of works (bridges, &c.). 7. Making mechanical drawings. 8. Principles of projection, perspective, and shadows.

IV. ESTIMATING.-1. Taking out quantities from drawings. 2. Measuring quantities from the works themselves. 3. Measuring artificers' work. 4. Calculating, measuring, and valuing earthwork. 5. Estimating value or cost of works.

V. SETTING OUT WORKS.-1. Centre-lines and side-widths of railways, roads, canals, &c. 2. Setting out bridges, viaducts, walls, &c. 3. Setting out tunnels and driftways.

II. GENERAL CONSTRUCTION.

I. STATICS.-1. Composition and resolution of pres2. Moments of pressures. 3. Parallel pressures, and the centre of gravity.

sures.

II. STABILITY OF STRUCTURES.-1. General con

ditions of stability. 2. Stability of polygonal framings. 3. Equilibrium of arches. 4. Stability of abutments and piers. 5. Stability of retaining walls. 6. Equilibrium of suspension bridges.

III. STRENGTH OF MATERIALS.-1. To resist a ten

sile and crushing strain. 2. Elasticity and elongation of bodies subject to a tensile or crushing strain. 3. When subjected to a transverse strain. 4. Elasticity and deflexion of bodies subjected to a transverse strain. 5. To resist torsion.

IV. MATERIALS EMPLOYED IN CONSTRUCTION.-1. Metals. 2. Timber. 3. Natural stones. 4. Artificial stones, including bricks, concrete, and the various cements used in masonry. 5. Materials for earthworks, such as embankments, puddled banks, dams, &c. 6. Materials for roads and pavements. 7. Materials for covering roofs.

V. DIFFERENT KINDS OF CONSTRUCTION.-1. Brickwork. 2. Masonry. 3. Forming Foundations. 4. Carpentry.

VI. AUXILIARS EMPLOYED IN CONSTRUCTION.

1. Scaffolding, fixed and travelling. 2. Centerings.

3. Coffer-dams.

III. MECHANICS, OR CONSTRUCTION OF MACHINERY.

I. DYNAMICS.-1. Vis viva, momentum, and work. 2. Motion; uniform, accelerated, or retarded; gravitation. 3. Collision and impact of moving bodies. 4. Motion down inclined planes and curves. 5. Motion about fixed centres; centres of percussion, oscillation, and gyration.

II. MOVING FORCES.-1. Water as a mechanical agent. 2. Air as a mechanical agent. 3. Animal strength as a mechanical agent. 4. Heat as a me chanical agent; the steam-engine.

moves.

IV. THEORY OF MACHINES.-1. Elements of machinery. 2. Teeth of wheels, racks, and pinions. 3. Transmission of work by machinery. 4. Determining the modulus of a machine in motion. 5. Mechanical expedients for transmitting or changing motion. 6. Proportioning the strength and dimensions of machinery.

V. HYDRAULIC ENGINEERING. I. HYDRAULICS.-1. The science of hydrostatics. 2. Hydrodynamics. 3. Pneumatics.

IV. SPECIAL CONSTRUCTION. I. COMMON ROADS.-1. Principles which should control the selection of route. 2. Laying out roads, and arrangement of gradients. 3. Construction of roads. 4. Draining roads. 5. Repair of roads. 6. Protecting their surface by different kinds of pave

ment.

II. RAILWAYS.-1. Principles which should determine the route, and the general arrangement of the curves and gradients. 2. Different systems of haulage; the locomotive, the atmospheric, and the rope. 3. Of the general construction of the railway. 4. Of the permanent way; different forms of rails, switches, &c. 5. Of draining the line, and maintaining the slopes and permanent way. 6. Arrangement of termini and stations. 7. Construction of engines and carriages. 8. System of working the line.

III. CANALS.-1. Principles which should determine the choice of the line of a canal. 2. Arrangement of levels; number of locks, and form of section. 3. General construction of canals. 4. Arrangement of locks; means of saving water, and obtaining feeders. 5. Methods of propulsion, or towing, and resistance on canals. 6. Construction of aqueducts. 7. Repair and preservation of canals.

IV. HARBOURS AND DOCKS.-1. On the construction of piers, breakwaters, and quay walls. 2. On the means of deepening harbours, by dredging or excavation. 3. Selection of site for docks, and their arrangement. 4. Construction and arrangement of locks, cast-iron and timber gates, sluices, &c. 5. Construction of dock walls.

V. BRIDGES.-1. Selection of site, and determination of the kind of bridge. 2. Construction of stone and brick bridges. 3. Construction of iron and timber bridges. 4. Construction of suspension bridges. 5. Construction of railway viaducts. 6. Of forming the foundations of bridges.

VI. TUNNELS.-1. Determination of the form and dimensions of the tunnel. 2. Method of excavating and securing the ground. 3. Sinking shafts, and

III. SUPPLY OF WATER TO TOWNS.-1. Principles which should guide the choice of the means of supply. 2. Different sources of supply; from the water-shed of the country, from springs and Artesian wells, or from large rivers. 3. Means of estimating the quantity required, and of ascertaining the probable supply and the quality of the water. 4. Systems of supply; the constant or high-pressure system, and the intermittent. 5. Selection of site for reservoirs. 6. Construction of reservoirs. 7. Contriv ances for raising the water to the level of the high reservoirs. 8. Of the means of filtering and purifying the water, and of the construction of the filter beds. 9. Of the motion of water in pipes, and their discharge.

IV. MARINE ENGINEERING.-1. Action of waves and currents; their modification by the contour of the shore, and the depth of water. 2. Their action on the shore, on beaches, on vertical, sloping, and curved walls, and generally on any obstacle. 3. On the régime of coasts, and their preservation. 4. Construction of sea-walls, embankments, breakwaters, piers, and other structures exposed to the action of the sea, more particularly as regards their form. 5. Principles which should determine the selection of the site for a harbour, and the arrangement of its form. 6. On the causes which produce shoals and bars. 7. Means of keeping harbours free from such obstructions, or of removing them where already existing. 8. On the improvement of harbours and sea channels.

V. IMPROVEMENT OF RIVERS.-1. On the tidal wave at the mouth of rivers, and its modification in passing up the river. 2. Principle of the conservation of tidal force. 3. On the antagonist agencies of the tide and land waters in rivers, and the means of determining which of these should be assisted; of the régime of rivers. 4. On the form of the shoreline of rivers, and their improvement. 5. Of the junction of rivers. 6. On the velocity of the stream; its scouring and transporting power compared with the nature of its bed. 7. Effects of projections, irregularities, and obstructions, such as dams and weirs. 8. Of the formation and removal of shoals; their causes; of artificial scouring and sluicing. 9. Of the shoals formed at the mouths of rivers; their cause and prevention.

the mac of the LOVE Í MATIA HAS palaf the at sa tu I not essence, zad fantasted it ones, by the dewing LEDATA DELLA a uzaz to the fue ara In the second pure there is the fal fil mng, the prer's toci sa a wistaore frm via 1.27.69 LITE 33 X LLP 1 SADD

work, but one of a minute: pile of benz Grace A Jy a sever use of tools in the bands Gismilla në mbaron are needed, a .. as a great decree of skill and taste in transferring the s.ject to the new marm but orgina, ideas are not required: this, thenfire, mast of terenity be ranked as a sail an-asefil, as whing diffusive of the pleasure ocuveged by the fine arts; and likewise useful, as airing a fi of remanerative labour to thousands of individuals who may be constitutionally unfitted for other employments.

But while engraving must this take its place among the useful arts, yet it must not be denied that in order to have the true spirit of the subject conveyed to an engraving, something more than ordinary skill and successful imitation is demanded of the engraver.¦ It has been well remarked by a tasteful writer,' that | "the engraver is to the painter, what the translator is to the author. As it is impossible to give a spirited translation of a work of genius without a portion of the author's fire, so it is essential to a good engraver that he should feel and understand the character of the original, and be initiated into the art of drawing, that his copy may at once be correct and spirited." But for this gift displayed in the works of many of our best engravers, we should still fail of the enjoyment the art is calculated to produce in the faithful rendering of the pictures of the first masters, and the multiplying of such instructive specimens in

our various homes.

The art of engraving is of extreme antiquity. If it cannot with any certainty be traced to antediluvian times in the case of Tubal-cain, the son of Lamech, who is spoken of as "an artificer in brass and iron,"

(1) Allan Cunningham.

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fans ni mesenly advanced

Ta ezust Toes a that mined nation was inte iplomatum Í macs in metal plates. Spect is f the arm is praised in Eruma ve thungu” to be of a Tery remote sangung, and are quite capable of being prated from as has been perred by actual experBut the Lira of in these rade outlines vra să and tieng impressives from them, Ti reserved to later times. Is the dents just missed a servery which now firms the principal element of our progress. This is the more remark alle when we remember that they knew how to take mpressies of seals and stamps in wax, clay, and other siû bodies, and that they seem to have had stamps with separate letters engraved upon them.

The art of engraving comprises three great divisons, for which appropriate technical terms have beca found by referring to the Greek language. Copper-plate engraving is named Chalcograrky, from the Greek words signifying opper, and I inscribe; wood-engraving, Aylography, from wood, and I isscribe; engraving on stone, Lithography, from a stee, and I inscribe.

The first of these, or the art of engraving on copper, and taking impressions from the engraved plates, is ascribed to a native of Florence, named Fai guerra, who flourished in the fifteenth century. He was a skilful workman in a species of handicraft then largely practised, namely, the engraving of church ornaments and other articles, and filling the engraved parts with a black composition of silver and lead. This was called working in niello, and had a good effect, as may be seen by remaining specimens. It is said that Finiguerra having on one occasion cast some melted sulphur on his engraving, to try its effect previously to putting on the black composition, observed, on removing the sulphur, that some dust and charcoal which had gathered in the hollows gave an impression of what he had engraven. On this be tried the effect of moistened paper, pressed down on the engraving with a roller, and met with complete success. Other goldsmiths and engravers followed

in the steps of Finiguerra, and this important discovery soon became widely diffused. Throughout the sixteenth century improvements in this art were numerous in Italy, and the skill of Marc Antonio Raimondi, and the students of his school, raised the fame of the Italian engravers to a high pitch.

Meanwhile Germany was making rapid progress in the same art, first practised in that country by Martin Schongauer, and carried to eminence by Albert Durer and his followers. The artists of the Flemish and Dutch schools, together with the skilful engravers of France, also contributed to spread throughout Europe the triumphs of this interesting branch of knowledge.

The art of engraving was early known in England. Printing was discovered during the first half of the fifteenth century, and engraving quickly followed, as is proved by Caxton's "Golden Legend," printed in 1483, and ornamented with numerous cuts. Copper-plate engravings appeared in Vesalius's "Anatomy," printed in England, in Latin, in 1545. These were the work of Thomas Geminus, or Geminie, the first English engraver of whom we have a distinct account. A translation of the work by Udal, dedicated to Edward VI., contained in the preface the following passage: "Accepte, jentill reader, this Tractise of Anatomie, thankfully interpreting the labours of Thomas Gemini the workman. He that with his great charge, watch, and travayle, hath set out these figures in pourtrature, will most willingly be amended, or better perfected of his own workmanship if admonished." The first maps of English counties were engraved by Christopher Saxton in 1579.

In the reign of Charles I. an engraver-royal (Voerst, a native of Holland) was appointed, and the art received much encouragement from the king and the Earl of Arundel. The celebrated Vandyke assisted its progress by his vigorous and expressive etchings; various improvements were made; Prince Rupert discovered mezzo-tinto, and for a brief period engraving flourished greatly; but the bad taste and dissolute manners of the succeeding reign checked its progress, and had the worst effect on the art. Its subsequent revival and brilliant success in the hands of Hogarth and his cotemporaries, and its high eminence at the present day, present too extensive a field to be traversed here. Suffice it that we describe some of the processes of this interesting art as now practised.

Supposing a copper-plate engraving to be begun and carried on without the aid of etching, it is as follows:-A plate of copper is first prepared, smooth, and free from all imperfections, very level, and highly polished. On this plate the outlines of the landscape or subject to be engraved must be accurately drawn. To this end the copper-plate is first heated in an oven till it attains a sufficient uniform heat to melt white wax, a piece of which is rubbed over it, and allowed to spread in a thin layer till the whole surface is equally covered, after which it is left in a horizontal position till the wax and plate are cold. In the interval a careful tracing of the original design is made with a black-lead pencil on thin tracing paper,

and this is afterwards spread over the waxed surface of the plate, with the lead lines in contact with it. The tracing being secured in this position, heavy pressure is applied, the effect of which is to transfer the lead lines from the paper to the wax. The engraver now takes a fine steel point, and (the tracing-paper being removed) goes over the subject lightly, so as just to penetrate the wax and touch the copper. By this means a perfect and delicate outline is drawn upon the plate, and when the wax is melted off, the subject is ready to be proceeded with and finished off, according to the skill and manual dexterity of the engraver. These are not within the powers of description; but we may briefly state that the principal instrument employed is the graver or burin, made of steel, and ending in an unequal-sided pyramidal point. This instrument is held in the hand at a small inclination to the plane of the copper, and is pushed forward in the direction required, to cut the lines on the plate. See Fig. 863. Should the lines be cut too

Fig. 8C3.

deeply, a smooth tool, about three inches long, called a burnisher, is employed to soften them down, and to burnish out scratches in the copper. But the graver, in ploughing furrows in the surface of the copper, raises corresponding ridges or burrs; these have to be scraped off by another tool, about six inches long, called a scraper, also of steel, and having three sharp edges. A woollen rubber is also occasionally used, with a little olive oil, to clear the face of the plate, to show the progress of the work, and to polish off the burr. Writing-engravers also use a leather bag, filled with sand, as a cushion, to support the plate during the progress of the work. Where a series of parallel lines are wanted, in architectural subjects or for skies, manual labour can be dispensed with, and a ruling machine substituted, which acts with most complete effect. The above method was the ordinary one in former times, and is still continued in the engraving of letters, silver plate, &c., but since the discovery of etching it has almost universally given place to that freer and more expeditious process.

Besides engraving, properly so called, there are several varieties known, as etching, mezzo-tinto, aquatinta, &c.

Etching now forms a most important part of the engraver's art, for nearly all his productions are commenced, and, to a considerable extent, carried forward by its aid. It is the process of corroding with aquafortis the lines of a drawing, traced out with an etching needle on the copper-plate, over which has been previously placed what is called an etching ground, namely, a preparation of bees'-wax, Burgundy pitch, &c., incorporated over the fire, and capable of resisting the action of the aquafortis. The following composition forms a good etching ground :-two ounces of