machine is $750. This machine will make 20,000 bricks per day of ten hours.

Fans should not be used for directly drying any kind of clay products, but they may be employed effectively in all classes of driers to gradually but constantly exhaust the air from the top, thereby at all times stimulating an active circulation among the wares.

When the green fire-bricks made from tempered clay are sufficiently hardened to stand the necessary handlings, they are pressed edgewise in a hand-press in which the mould-box is arranged, as shown in Fig. 106, which is for nine inch firebricks, and the price on board in Philadelphia, Pa., is $125.

The press shown in Fig. 83, page 225, can also be used for pressing edgewise, and the manufacturers of the machines

shown in Figs. 84 and 86 also make presses suitable for this work.

The care to be observed in drying materials for retorts and crucibles has already been enlarged upon.

The setting of fire-clay products is very carefully done, all stock is gently handled, and when it is in the shapeof fire-bricks they are arranged or placed in the kiln in a manner much similar to that employed for common bricks in the same locality in which they are made.

The placing of wares of various shapes in a kiln preparatory to burning is a matter for the exercise of judgment, and requires experience as well as discretion. One piece must be made to securely prop another without having too much of their surfaces in continued contact. Heavy pieces form the base or supports, and the lighter wares are variously distributed, care being observed to allow the steam or "water smoke" every opportunity for freely escaping, and the heat to have regular distribution throughout the entire pile of wares.

If large openings are left one over the other, "flues" will form, and the heat will, during the whole time of burning, quickly rush and circulate among these "flues," thereby causing all the stock exposed in them to be burned unequally, extremely hard on one face and not so much on another.

The loss from cracked and twisted wares caused from careless setting or placing in the kilns is often very large, being much greater in fact than it would be by using extra precaution to avoid "flues" in the setting.

But the "flues" are sometimes, but not so often, formed

from the unequal shrinking of the stock in the kiln, which is an additional reason for having a uniform mixture of the materials.

The circular, domed "over-draft" kilns are largely used for burning fire-bricks and terra-cotta products, and the Hoffman annular kiln is also employed extensively in all parts of the world.

Both of these kilns are so commonly known, that there is no necessity for an explanation of their construction in this volume.

The over-draft kiln shown on page 152 can be used to advantage in the burning of fire-clay wares, as well as for common bricks.

Kilns constructed on regenerative principles are now coming largely into use for the burning of fire-clay products of all descriptions, as it can be performed in them cheaply, thoroughly, and more effectively than in any other class of kilns. They are to the uninitiated complicated; but when fully understood are more simple in their workings than the old styles of kilns.

Mr. James Dunnachie, of the Glenboig Star Fire-clay Works, Lanark, Scotland, has recently perfected an improved regenerative kiln for burning fire-bricks, which has for its object more thoroughly to mix the air and gas burned in such kilns, and to effect a better diffusion of the heat obtained from their combustion, as well as more thoroughly to regulate and equalize the same. These objects are effected by constructing in the walls of adjacent kilns duplex hollow spaces or flues, the alternating portions of the opposite sides

of which have slits or perforations formed therein, so as to enable the heated products of combustion to be passed or discharged from the lowest part of one kiln into the lowest part of the next kiln-that is to say, the kiln which is being heated preparatory to being fired. These flue-spaces are provided with vertical or horizontal dampers, so as to shut off the communication between the kilns, the slits or perforations in the flue-spaces effecting the improved diffusion. In place of forming such flues in the walls of adjacent kilns, flues may be formed in the brick-work outside the wall, in which case the air descends some distance below the floor of the kiln, where it passes through ports, regulated by dampers, into a still lower flue, from which it escapes through slits or perforations formed in the lower part of the walls into the burner or chamber, or opening, wherein it mixes with the gas. For the purpose of admitting either hot air into the upper part of the kilns from an adjacent kiln, or for the purpose of admitting cold air to the upper part of a kiln being fired, a similar flue-that is to say, either duplex or single-is provided with dampers and with slits or perforations in its opposite sides in the walls at or near to the upper part of the kilns. Either hot or cold air is admitted through these upper flues and slits or perforations, when the air admitted at the lower part of the kilns with the gas may be either deficient in quantity to produce complete combustion, or when the temperature of a kiln at its upper part may be either too high or too low. In place of making the flues duplex, with slits or perforations, as before described, they may be made single, with one side

namely, that through which the discharge takes place-constructed with one, two, or more larger openings in lieu of slits or perforations above or at a level with the bottom of the kiln, and with slits or perforations at the opposite side. The improvements before described may also be applied to calcining-kilns and other analogous apparatus.

Figs. 107 to 119 represent the invention as applied to kilns arranged in two opposite rows or series of five (less or more) each, the end kiln of each series being connected to the corresponding end kilns of the other series by means of flues; but it may be applied to kilns otherwise arranged.

Fig. 107 is a general plan of the series of kilns. Fig. 108 Fig. 109 is a front elevaFig. 110 is a longitudinal 111 is a plan of the same,

is an end elevation of the same. tion of one of the series or rows. vertical section of the same. Fig.