between them. The steam way pattern, fig. 10 is set in its place in an inverted position, resting on the flanch i. Its precise position will be ascertained by the loam board, which ought to touch it when passed round. The building is commenced upon the cope ring; and, having been raised above the flanch i, another ring k, is bedded on the building, lying near into the loam board, with a segment cut out of it sufficient to clear the steam way pattern on both sides. Upon this ring the building is continued till near the under side of the exhaust passage, at which place a similar ring 7, is bedded on the structure, overhanging it sufficiently to sustain the building round the passage, at which place it is greater in diameter. Having built up the height of the passage indicated by the board, a layer of loam on the top is swept flush with the upper side of the projection by means of a transverse stick nailed on the board. This forms a parting surface, by which the cope is divided into two parts, the necessity of which is apparent on considering the method of placing the cores for the exhaust passage. After blackwashing the surface, a third ring m, with projecting snugs on its rim, is laid over it, being faced, however, with a layer of loam to protect it from the melted iron. The building is continued upon this plate till it reaches the top, when it is succeeded by another plate n, of a square external form, and somewhat larger than the square base plate of the casting immediately over it. The building is finally carried up to the horizontal piece b, which smooths off the upper surface with loam.

It will be remembered that the mould is on one side, cut longitudinally throughout, by the pattern of the steam ways. On that side, therefore, it has to be completed; this object is attained by providing a cast-iron plate, done in open sand, fitting generally the interior of the pattern, and having three openings through which the core prints are passed when the plate is applied. It is daubed all over the inner face with stiff loam, and being set up in its place, the loam receives the impression of the face of the pattern. Lastly, the square flanch pattern is laid over the whole, upon the bed prepared for it; preceded by the four stiffening flanches, and is surrounded with additional loam, flush with its upper side, to form a bearing for the top plate.

In the manner thus described, the external figure of the cylinder is formed. The whole mould from the bottom is lifted by the snugs on the cope ring h, off the core ring, upon which the two layers e and i, are left. It is conveyed to a sufficient stove to be thoroughly dried.

This is an operation comparatively simple, as the core is but a simple cylinder of brick and loam. In the first place, as the loam flanch i, has formed its impression on the interior mould under the plate k, it is of no further use, and is, therefore, broken away, leaving the bearing clean to receive the core, as represented on the left side of fig. 12; o, is the loam board in its proper position for working, having its inner edge set parallel to the spindle, and to the diameter of the cylinder required, and simply fixed to the arm at the top. A cylinder of brick work p, is first built up, being every where an inch or so clear of the board. A coat of loam s, is next laid on as usual,

1

to fill up the clearance, and complete the core.

The board and the

spindle being removed, the work is lifted away to the stove on the core ring a a, by the snugs upon its rim.

The next business of the moulder is the formation of the smaller cores, which are to form the winding steam passages to the cylinder, of which there are three; the two supply passages a a, and the exhaust passage b. The two former being of the same shape, may be formed from one core box, seen in plan and section at fig. 6, in which a, indicates the core boxes; for such kinds of cores are usually formed on three sides, and open on the fourth side to admit the material, which is shaped off on this side by the edge of a piece of wood cut to the contour of the core, and drawn along upon the sides of the core box as guides. The core for the exhausting way is partly circular, and partly otherwise at the ends. Its formation is thus more complicated than that of the other cores. It is made in three parts; the centre part annular to embrace the cylinder, and formed by a loam board, and the terminations made in core boxes, and fitted to the other; fig. 14, is a vertical view of the method of making the annular core. It is built upon a portable square table, convenient for small, circular work generally, as it may be conveyed to the stove without the necessity of shifting the centre. The spindle turns by a conical pivot on its under end moving in a socket, which is the only staying it requires. A block a a, is first prepared, being a plain built ring of which the exterior is smoothed with loam, and is made exactly to the interior diameter of the core, and to the same depth. The core seen in section at b, is run upon the outside of the block to the necessary thickness, in the course of which two wrought-iron angular rods are imbedded. in the core to impart their stiffness to it. At b', is shown the valve face portion of the core, (at c, fig. 8,) of which c, is the box for making it in section. The round core for the short, straight passage d, fig. 16, is made of loam, being run up on a short iron centre.

In the making of these small cores, as in that of green sand, it is necessary that they be strengthened with iron rods bent to their form, so as to pass through the heart of them, and finished with eyes at the outer extremities, for locking them to the face plate. An open passage, running through each core, is formed, as in green sand cores, by laying pieces of cord along the irons. These passages are of great importance, as, upon them depends the escape through the openings in the face plate, of the otherwise confined air existing in the mould, while the metal is being run. The too close proximity of these passages at any point to the surface of the cores must be well guarded against. In such a case, the melted metal in contact with the core breaks into the interior of it, and intercepts the air in its escape, which aggravates the evil, by forcing it into the body of the metal, and thus rendering the casting unsolid. The accident even assumes, in some cases, a more serious aspect, by causing such an agitation in the metal as to render the cast utterly useless; indeed, we have even seen the metal already poured almost wholly expelled from the mould, and sent in showers through the foundry, the occurrence being entirely attributable to an oversight of the nature referred to. VOL. VII, 3RD SERIES-No. 4.-APRIL, 1844.

22

Fig. 15, is a side view, in section, of the mode of placing and fixing the cores a a, for the steam ways to the cylinder; qq, is the face plate lined with stiff loam, which retains the impression of the steam way pattern; a a, are the two cores, the nearer ends of which are passed through the openings made in the plate for them, and fixed there by small rods passed through the eyes of the stiffening irons. The ends are made with shoulders which bear upon the upper side of the plate, fig. 15, which may be understood from the form of the prints in fig. The horizontal parts of the cores a a, fig. 15, are supported at their proper distance off the loam work beneath them, by steeples stuck into it.

10.

The mould and the cores having been well dried, they are dressed and smoothed where necessary, and finished with a coat of coal powder. Fig. 16, is a vertical section of the whole mould, showing all the parts fitted to one another, so as to contain among themselves the vacant space indicated by a white ground, into which the metal is delivered. The mode of depositing and putting together the mould is as follows: the main core pp, is lowered upon its rings, from which it is never separated, into a pit dug in the floor of the foundry sufficiently deep to receive the core below the surface. The exhaust passage core is next deposited in its exact position in its place on the top of the lower part of the cope, being sustained in the usual manner off the core by chaplets made of two pieces of strong hoop iron, riveted on the ends of two studs, so as to have the necessary thickness of space. The lower part of the cope, thus furnished, is next lowered over the main core into its place upon the core ring, thus surrounding the core, and containing within it a space between, as indicated in the figure. Another set of chaplets are deposited upon the exhaust core, which, by being in contact with the upper half of the cope when placed above, prevent the core from floating off its seat when immersed in the fluid metal. This is a matter of greater moment than the sustaining of the core from below, as will be apparent on considering the great difference of specific gravities of dry loam and iron. In this case the upward effective pressure of the fluid metal upon the core, is proportional to the difference of their specific gravities, which being so much in favor of iron, the pressure upwards, sustained by the chaplets, cannot be much less than the weight of a body of iron of the same bulk as the core. Therefore, as a safe general rule, chaplets are, or ought, to be made of sufficient strength to resist the weight of a body of iron equal in bulk to the core, for the support of which they are destined.

The upper part of the cope having been let down into its place, the face plate with its cores fixed to it, fig. 15, is let down in front of the vacancy in the side of the cope, till it arrive at the proper height, when it is set close into its place, and the end of the exhaust core b, receives d, through the middle opening in the plate, and secured on the outside by the eye. The branch core d, is then set in, and supported on chaplets, and over it a ring, or cake, of loam ml, seen in section in the figure, is placed, being strengthened internally with