80G SODA.— Black

this class), the hand furnaces will continue to holdtheir ground.

The diagrams on Plate III. represent workingdrawings of a hand hall furnace of the very bestconstruction as used on the Tyne. There are, ofcourse, minor deviations in details in every factory,but the principle is always the same. At one end isseen the fire-place, which is generally from 2y to 3feet wide, and from 5 to 6 feet long. The fire-barsare plain wrought-iron bars, 2 or even 3 inchessquare, resting loosely on three horizontal bearers,which are either formed by strong bars laid on oneedge, or by strong railway plates. Another hori-zontal bar is often inserted lower down, to form arest for the poker during the laborious operation of“scarring” the fire at the end of the shift.

The above simple and somewhat rough arrange-ment is preferred to any complicated system of fire-bars and fire-places; because the latter are found togive way very soon in actual work, through the“scars” or “clinkers” of the coals adhering to thebars. In the above arrangement of loose bars the“ scars ” can be removed from time to time byshifting the bars and working the large pieces downinto the ash-pit by means of large pokers and scar-hooks. This operation is greatly facilitated by the“ cave ” under the fire-place shown in the diagram.This is not used in all factories, but only in aportion of them ; but the writer can testify to thegreat advantage of using it, not only in the aboverespect, but in several others. There is always awater-tap near the cave to quench the ashes and“scars,” and to keep the grates comparatively cool;and the cave allows the water to stand regularly inthe bottom of the fire-place. The back of the fire-place is frequently stepped back, as shown in theplate, so that the flame can travel along thewhole length of the fire-bridge. The latter is a veryimportant part of the furnace; it must be very strongin order to resist the burning coal on the one side,and the fluxing ball-mixture on the other side. Thelatter penetrates deeply into the furnace beds, andwould soon flux away into the fire-place and stop upthe latter, if no precaution were taken against this.The precaution consists in building a strong cast-ironplate (1£ to 2 inches thick) in the fire-bridge, whichdams back die fluxings, and does not allow them topass; and as the “bridge-plate,” as it is called, wouldsoon be melted or burnt in its own turn, if it weresimply put in a solid wall, it is protected by an air-course on the side next to the fire-place. The greatheat within the bridge continually causes a flow ofcold air to rush into the air-course, and thus pre-serves the plate for a very long time. Manyattempts have been made to utilize this heated air,by conducting it into the inside of the furnace or thefire-place, and in theory this is no doubt an excellentthing, as the heated air will give a much hotterflame than the cold air entering through the gratebars; but unfortunately all such attempts have failed,because the openings, through which the heated airis to escape, are soon fluxed up or blocked up bydust.

:-ash Furnaces.

The real working part of the furnace is generallydivided into two beds, as in the Plate, rarely intothree. It is formed by building a 9-inch wall of thevery best fire-brick from a depth of 12 inchesbelow the first or working bed, to a height of 15 or18 inches above the same; this wall goes all roundthe inside of the furnace, and follows the curvedlines shown in the horizontal section. Its left sideforms part of the fire-bridge, its back the lining ofthe furnace back, and its front is pierced for thetwo working doors. Within this wall is put a layerof ground fire-clay or of dried and ground chalk, 3inches deep, leaving 9 inches to the top of the bed.These 9 inches are taken up by a course of thehardest fire-bricks on end, wedged closely togetherwithout any mortar, and only grouted in at the topwith fire-clay. This 9-inch course forms the workingbed proper; it is always sloped a few inches from theback towards the working door. The back bed, or“shelf,” is a few inches higher than the working bed,and is sometimes only formed of bricks on edge,5 inches thick. The corners of the furnace, andmore particularly its front part altogether, arebevelled off, so that the men can reach every part ofthe bed with their tools. The doors (both of thefire-place and of the beds) are sometimes onlyclosed by loose iron plates; but it is much better toprovide them with fire-clay lumps, inclosed by an ironframe and hung from pulleys with balance weights.The arch of the furnace is generally more or lesssloped towards the end of the furnace. The furnaceis, of course, strongly bound with uprights (mostlyformed by double-headed railway rails) and cross-rods ; the upright binders are sometimes let acertain depth into the ground ; sometimes, however,they are connected at the bottom by cross-rods aswell as at the top, and channels are left in the brick-work for that purpose. In some cases the cross-rodspass through the upright binders; they are thenscrewed at their ends and fixed with nuts; in othercases they are formed into loops, and driven on tightby means of iron wedges. In a few cases strengthis sacrificed to ornament, by making the uprights nohigher than the furnace walls, and bending the rodsalong the crown of the arch. The constructionwhich is shown in Plate III. is much strongerand also more usual.

On the Tyne it is usual to case the whole furnace,back, front, and end, with 1 inch metal plates, whilstin Lancashire only small strips of iron (5 inches Xa inch), are placed behind the binders. The formerplan is of course much stronger; and although morecostly in the first instance, it is cheaper in the end,as the plates last nearly for ever, and the furnacesstand much longer.

In Plate III. a hopper is shown over theworking bed, through which the ball-mixture isintroduced into the furnace. This presupposes anarrangement of over-head tramways for chargingthe furnaces; where such an arrangement does notexist, the ball-mixture is charged by shovelling itin through the door of the back-bed. This causesmore labour, takes more time, and cools the furnace