upon the grate C. The aprons E incline toward the ashpit door F, so as to cause the ashes and cinders dropping upon the aprons to slide forward toward the ash-pit door, and the hinging of the aprons to the grate-bars enables the front ends of the aprons to be raised, so as to permit access to the fuel placed upon the ground between the grates C C.

G is the fire-door, hinged to the frame B, and provided with vertical slots or openings g, which are opened and closed by a sliding plate g', in the manner of an ordinary register.

His a protecting-plate, arranged on the inner side of the fire-door G, and connected thereto by stay-bolts h in the usual manner. i are vertical slots or openings, arranged in the plate H in such manner that solid portions of the plate Hare opposite the openings g of the fire-door G, and the openings i opposite the solid portions of the fire-door. This construction of the protecting-plate H causes the air-currents entering through the openings g of the fire-door to impinge against the solid portion of the plate H, which, being kept at a very high temperature by the fire upon the grate, heats the air before it enters the arch, thereby preventing the bricks from becoming checked.

The grates C may be charged with wood or coal, and the space C1 between the grates is preferably charged with wood or coke. By admitting a strong air-current through the fire-doors G, the flame and hot gases are driven from the grates C toward the centre of the kiln, and the combustion of the fuel between the grates is accelerated. Upon closing the damper in the fire-door G, the hot gases from the grates

In this matter architects owe a duty to themselves no less than to their clients and the public. It is not the province of this volume to attempt an explanation of this phenomena, which is a matter of common observation.

In newly completed buildings a little drapery hung up for a few months may often retard reverberation and be a great aid; it can easily be removed when the moisture disappears from the walls, and the acoustic properties are assured.

Since dry structures cannot be built with bricks that are very absorbent, and as the extent to which bricks absorb water is so important, it is worth while to give a little attention to this subject in the different classes of brick-machines.

The bricks produced by all dry-clay machines absorb much more water than do those produced by any of the other machines.

It is not the intention in this work to canvass and give the merits or demerits of any particular machine; but by saying what has just preceded, merely to hint at a few of the considerations which should govern those who part with their money for the purchase of either the stock produced, or for a machine itself.

The process of manufacturing bricks by machinery may be divided into five stages, viz:—

Preparation of the clay.

Shaping the brick.

Drying.

Setting.
Burning.

The clay is not dug in the winter and exposed as for

hand-made bricks; but for dry and damp-clay machines the clay is taken directly from the bank, and for dry-clay machines is hauled under large sheds and allowed to dry; but for the damp-clay machines it is hauled directly to the mill which is to prepare it for the brick-machine. The difference between dry and damp-clay bricks is in the condition of the clay when it is granulated and moulded.

It requires a much stronger machine and greater power te shape the dried clay into bricks than it does for the dampchy, as the pressure must be tremendous in the first case, and it need be but normal in the second condition, provided the pressure is exerted while the mould-bed is at rest.

Disintegrating mills for clay may be divided into two classe, the first being those which granulate and sieve the clay at the same time; and the second class being those which granulate without sieving. Sometimes there is a combination of the whole of the latter class with some portion of a mill of the first class; but the result of the combination is usually a mill of the first class.

A combination of the two principles is made when the rolls are placed in position above the grates of the mill, and instead of the clay being pulverized and forced through the grates by a heavy revolving roller, the clay passes through the elevated and stationary rolls, falls upon the fixed grates, and is agitated and forced through them by revolving clayploughs, drags, and other contrivances.

Sometimes, as is shown by the drawings of the clay-pulverizing machine, which will be immediately described, the clay passes through the rolls and the grates are made to

revolve, and the clay falling upon them and coming in contact with the fixed irons extending over the grates, is forced or sieved through them.

The machine shown in Figs. 46, 47, 48, and 49 is in daily use in a large brick-yard in Washington, D. C., and is the invention of a practical brick-maker of that place, and it

is for pulverizing clay for making brick of the kind known as "damp-clay," but by a slight modification, which will be described, it may be made to temper the clay after it has been pulverized.

In Fig. 47 the teeth of the revolving grate E' are shown too close to the grates, and it was found that they were liable to clog with the clay from the grates; but this was obviated by increasing by six inches the height of the rim. E2 over that shown in the drawings.

Figure 46 represents a plan or top view of the machine; Fig. 47 a front elevation; Fig. 48 an end elevation; Fig.

49 a sectional view of the crushing-rollers and device for removing gravel-stones from the same.

A is a box or frame upon which the main portion of the machinery is mounted. B and B are two cast-iron crushingrollers, made to rotate toward each other by gear-wheels bb.

The machine may be driven by any suitable power applied to the crank-wheel C on the shaft of roller B. D is a pointed scraper for removing stones which are too large to pass through the crushing-rollers. It is suspended from friction-wheels d d, which ride upon a horizontal rod or bar, d', above the crushing-rollers; its shank e passes between