venting the risk of breakage. The tool is capable of adjustment vertically by a vertical screw, and angularly by a tangent screw and quadrant, as shown in the front elevation. The horizontal slide, with the cutting tool and gearing, admits of a lateral motion, being fitted accurately to the upper surface of the foundationpiece, this lateral motion being imparted to it by means of a screw and nut. All the movements in this machine may, if it is desired, be fitted with feeds, in order to render it self-acting. We may here observe that the grooves in the chuck or table are undercut, in order to admit the heads of bolts, whereby the work is securely fixed. The usual driving gear is furnished to this machine.

We will now proceed with the description of a drilling machine, illustrated Plate VIII. This machine consists of a stout frame, carrying at its lower part a table or chuck capable of vertical motion, and at its upper part two arms, supporting the drilling gear. The driving riggers and accompanying gearing are similar to that exhibited on the head stock of the lathe previously described; but motion is communicated from the horizontal mandril to the vertical spindle by means of bevelled or mitred wheels, as shown. The vertical spindle is hollow, containing the drilling shaft, which has at its lower extremity a socket for the drills, and at its upper extremity a screw by which it is raised or lowered. At the back end of the horizontal driving shaft are some small speed pulleys connected by a strap with a similar series on a parallel shaft placed lower down, and having at its front extremity a short screw, which gears with a worm-wheel on the lower end of a vertical shaft, parallel with the drilling spindle. The upper end of this shaft carries a spur-wheel, which gears with another fixed to the nut, by which the screw attached to the upper end of the drilling spindle is raised or lowered; thus the machine is made self-acting. To the lower end of the smaller vertical shaft is fixed, as shown, a hand-wheel, so that the feed may be applied by hand, if required. This machine may be used either with drills or small boring bars, carrying cutters fixed in slots. The driving gear is of the usual form.

Plate IX. represents a planing machine. It consists of a stout bed or foundation-piece, furnished with two grooves. Upon this bed slides a table furnished with pieces, which fit the grooves. This table is caused to move rectilinearly by a pinion acting upon a rack attached to its lower side. This pinion is driven by gear.

ing connecting it with a driving shaft having three wheels or riggers, the centre one being loose and the outer two being so arranged that when the strap is on one wheel a slow motion towards the cutting-tool is obtained, and when it is upon the other wheel a rapid motion from the cutting-tool is obtained. The strap · is shifted at the end of each stroke by means of a pair of stops, clamped to the bottom of the table. These stops strike an arm on a shaft, throwing it backwards and forwards, whereby the motion is reversed and the requisite feed imparted to the cutting tool. Near one end of the bed a pair of stout frames are fixed, one on each side, connected at the top by a strong bracing piece. The front faces of the upright posts of these frames are accurately finished, and carry a long transverse slide, which may be raised or lowered by means of vertical screws outside the post, worked by bevel wheels gearing into others, fixed on a transverse shaft passing over the top of the frames. On the centre of the transverse slide is the tool-holder, fitted on a slide with a vertical adjustment, and also an angular adjustment. This slide may be moved horizontally or vertically by the self-feeding apparatus mentioned above; the former being obtained by means of a screw in the transverse slide, and the latter by a sliding bevel-wheel on a shaft in the same, which gears with another bevel-wheel on the vertical adjusting screw of the tool-holder. In this apparatus, as in the shaping machine, the tool rises at the return stroke of the table, the tool-holder working upon gudgeons. In order to plane the sides of wide work, tool-holders are attached to the vertical posts of the side frames or standards. The feed is applied by means of palls, the arms to which they are attached being worked by a vertical rod, which rises and falls according to the motion of the . shaft, by which the strap is shifted at the termination of each stroke.

Plate X. exhibits a view of a punching machine of peculiar construction. On one side of the apparatus is a punching, on the other side a shearing, arrangement. These are worked by levers, as shown, the punch and upper shearing edge being alternately raised and lowered by means of the cams, shown in dotted lines. These cams are upon a shaft carrying a large spur-wheel, to which motion is communicated by a pinion on the driving shaft.

Punching and shearing machines are generally made with ver

tical slides, as in the above apparatus; which, however, are driven by eccentrics working in rectangular spaces within them, of such dimensions that the width of the aperture allows for the lateral play of the eccentric; whereas the height of the aperture is equal to the diameter of the eccentric.

Messrs. C. De Bergue and Co. have patented an exceedingly ingenious punching and shearing machine. It consists mainly of a stout frame, containing within it a rocking-frame worked by an eccentric. The lower part of this frame is wide, carrying on one side a shearing edge, on the other a punch.

Mr. Cochrane, of the Woodside Iron-works, Dudley, has constructed some drilling machines, containing eighty drills each, to drill the plates of the railway bridge now in construction at Charing Cross. The feed is applied by hydraulic pressure. It has been found that with eighty one-inch drills plates five eighths of an inch could be economically perforated in fifteen minutes.

Besides the machinery already noticed, machines are made in which nuts and screws can be produced. They are fitted with easily moved slide rests, which rests are drawn along by the action of the threads following the cutting edges.

The nut-shaping machine consists of a table, to which is fitted a head stock and driving gear; upon the mandril is a rotatory cutter, with cutting edges on its face and also on its periphery. In front of this cutter is a circular piece of metal, formed with six or eight equidistant notches in its edge, into which a pall may be caused to fall, to retain the plate or chuck during the operation of facing one side. The top of the nut is faced by the periphery.

A dividing engine is a species of lathe with a divided chuck, palls falling into the divisions.

In addition to the machines described, other apparatus are frequently required for the execution of work of a peculiar character.

Some minor machines will be described whilst treating of the manipulations conducted in the workshop.

CHAPTER VI.

ON MANIPULATION:

In the present chapter we purpose to describe the manipulations with which the mechanical engineer must be acquainted in order to reduce rough castings and forgings to accurate forms, and to fit together and erect the machines of which those forms are the elements.

The most convenient method of describing these manipulations will be to commence with the rough castings and forgings, and follow them through the various processes which they must undergo previous to their completion. Let us commence with the casting of a steam-engine cylinder, with its covers and slides. The cylinder may first be fixed upon the bed of the lathe and bored, the boring being effected in the following manner. Let the boring-bar be placed between the centres, and fitted with a boringhead, in diameter nearly equal to the internal diameter of the cylinder. In this boring-head several cutters are fixed, the angles of the cutting edges being nearly 90°. By this means we may remove the greater portion of the excess of the material; but int taking the last cut, the lathe must not be stopped after the commencement of the cut until the completion of the same, and the cut should be taken by a point-tool, which will give most accurate results; for although the interior of the cylinder may look and' feel rough, it will be found after a few days of active working to have worn smooth, which will not occur so satisfactorily if the cylinder be improperly bored.

The ends or flanges of the cylinder may also be faced up before removing it from the lathe by cutters fixed to a slide attached to the boring-head.

The cylinder having been bored, it may be removed to the planing machine, where the port faces may be planed; in this, as in

the last operation, the finishing cut should be taken by a pointtool. These port faces will subsequently require further treatment to reduce them to a plane surface as nearly as possible; but we will now consider the preparation of the cylinder covers.

Each cylinder cover may be chucked in an ordinary lathe, turned on the edge, faced on the under side of the flange, and the upper cover bored out at the stuffing-box. The covers may then. be placed in position upon the cylinder, and the holes by which they are to be connected with the latter drilled under the drilling. machine.

We will next speak of the operation of facing the ports; we must, however, first pause to mention the instruments used by the. engineer to measure and mark out his work. The first of these, the dividers or compasses, are too well known to need any description at our hands. The callipers, intended for taking diameters and thicknesses, are similar to compasses, with curved legs; for taking thicknesses and diameters external, the legs should be bowed outwards, but for taking the width of recesses and internal diameters, they shonld be bowed inwards; but one pair may be made to answer both purposes. The mechanic will also require squares, straight-edges, and planometers, or surface-plates. Squares may be tested by ruling a very fine line, holding the pencil close against the edge of the square, then reversing the square, and drawing another fine line coinciding at some point with the former; then if the lines coincide throughout, the square is correct, if not, the contrary is the case. The straightness of the blade of the square may be tested in the same way as that of an ordinary, straight-edge, which is effected thus: rule a line as before, after. which turn the straight-edge end for end, make the two ends of the straight-edge coincide with the extremities of the line already ruled, then rule another fine line; if this coincides in every part of its length with the first line, then is the straight-edge accurate, but if otherwise, the two lines will contain a space, and as two straight lines cannot contain a space, the edge must be inaccurate.

It may be interesting here to describe the method to be pursued in making a straight-edge. Three straight-edges should be made together; for this purpose three strips of metal are laid side by side, and planed as true as possible; we will number them one, two, and three. In the first place, numbers one and two are filed