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Rh and thus passes alternately under it and over the moulds, conveying sufficient each time to fill the latter. The bricks are delivered from the moulds by the lower pistons, which are forced upwards by the complete revolution of the cams, and the newly-matle bricks are forthwith moved forward by the approach of the feed-box with a fresh charge of the material. In another dry-clay machine con structed by Messrs Bradley and Craven of Wakefield, two or three distinct pressures can be given to a brick, and by this means the air is gradually forced out from the interstices, and the brick consolidated to a greater extent than can be effected by a single pressure. The varieties of brickmaking machinery are too numer ous to be separately noticed, however briefly, but the fore going may suffice to illustrate the general principles involved in their construction. With suitable modifications, perfor ated or hollow bricks are frequently produced, on which there is a saving in cost of carriage, and also in mortar and labour.

Among the objects at the International Exhibition of 1874 there were several varieties of brick prepared with out burning, according to a process devised by Messrs Bodnier. They are made by intimately mixing certain materials of the nature of cements or mortars, and squeezing the mixture into the desired shape by hydraulic pressure in a specially-constructed machine. Sand and selenitic lime are the constituents of one kind of brick ; these substances, together with Portland cement, of another ; and a very serviceable kind of brick is prepared from blast-furnace slag, which, consisting chiefly of silicates decomposable by lime, is just as suitable for the purpose as the volcanic products, trass and pozzuolano, which have long been employed. The bricks give good results on application of the usual tests.

The old invention of floating bricks (known to Pliny) was completely lost till M. Fabroni discovered they could be made from the earth known as fossil meal, which is abundant in Tuscany, and is found near Castel del Piano in the territories of Siena.

For the drying and burning of bricks, the construction of kilns according to Hoffmann s method is a remarkable improvement of late years. These kilns are formed by a series of arched chambers connected by passages to one main chimney flue, each passage or flue having suitable dampers to regulate the heat at any desired point. Small coal, slack, or peat fuel may be used, which is fed in from the top of the kilns through small openings. The waste gases from the burning and cooling chambers are made to pass successively into other chambers and give out their heat before escaping to the chimney, thus completing the drying, and effecting a partial burning, of newly-made bricks before the actual firing of the chambers in which these latter are newly set. Such kilns are no doubt beyond the means of most brickmakers, but it is perhaps a question for consideration whether bricks must necessarily be burnt in immediate proximity to the spot where the clay is obtained. In an instructive report on the manufacture of bricks, drawn up a few years ago by a committee of the Manchester Society of Architects, the following points were specified as requiring attention, in order to improve the character of the common brick : (a) Greater care in cleaning the clay and in thoroughly tempering it ; (6) variation in the size of moulds, so as to produce uniform sized bricks from various clays; (c) moulding the brick with material of such consistency that it may not become misshapen by the effects of its own gravity ; (d) greater regularity of surface of the drying-ground ; (e) protection from extreme variations of temperature and rain in drying ; (/) less frequent and more careful handling in the process of drying, so as to preserve the edges ; (g) a means of burning whereby the amount of firing shall be under control. In experiments on the absorption and retention of moisture, it was found that the bricks which parted most readily with their mois ture at first were the longest in drying, and vice versa.

Tiles, being a thinner ware than bricks, have to be made of purer and stronger clay, and require more care in treatment, but the process of manufacture is not essentially different. The numerous varieties of tiles may be roughly arranged in three classes, viz., paving tiles, roofing tiles (including the flat plain tiles, the curved pantiles, hip, ridge, and valley tiles), and drain tiles. In weathering, the clay is spread in layers of about 2 inches thickness during winter, and each layer is allowed the benefit of at least one night s frost before the succeeding layer is put upon it. Sometimes the weathering is effected by sunshine. The comminuted clay is next placed in pits and allowed to mellow or ripen under water. Then it is passed through the pug-mill, and the tempered product, if necessary, slung (that is, cut in thin slices with a piece of wire fixed to two handles, in order to detect any stones), and then passed through the pug-mill again, after which it is generally ready for moulding. To take the case of pantiles (hand- moulded), the moulder turns the tile out of the flat mould on to the ivashing-o/ frame, on the curved surface of which, with very wet hands, he washes it into a curved shape. Then he strikes it with a semi-cylindrical implement called the splayer, and conveys it on this to the flat block where he deposits it, with the convex side uppermost, and, removing the splayer, leaves the tile to dry. The tile is afterwards beaten on the thivacking-frame, to correct any warping that may have occurred, and trimmed with the thwacking- knife. In the kiln, which is constructed with arched furnaces at the base of a conical erection called the dome, the tiles are closely stacked in upright position, on a bottom of vitrified bricks. The fuel used is coal, and the burning continues usually about six days. In making pipe drain tiles, the clay is first moulded to the proper length, width, and thickness, then wrapped round a drum ; the edges are closed together, and the tile is carefully shaped by the operator s hand, sometimes assisted by a wooden tool. Tiles as well as bricks can be made by machinery ; with suitable dies, almost any form of tile may be thus had, which is producible by the advance of a given section of clay parallel to itself. In other machines pressure is exerted on the clay in a mould.

The manufacture of tesserae and encaustic tiles has been brought to great perfection in recent times, through the enterprise especially of Mr Minton. It is a revival and extension of a very old art, which originated, probably, with the Greeks. The tesselated pavements of the Romans, of which many specimens are still extant, were formed of small pieces of stone or marble of various colours, bedded one by one in a layer of cement. The principle on which tesserae are now made, is that dry and finely-powdered clay, compressed between steel dies, is changed into a very com pact and hard solid body, a fact first observed by Mr Prosser in 1840. The solid pieces, which are thus pro duced in a screw-press, are enclosed in earthenware cases or pans, call saggers, and fired in a potter s kiln, after which they are icady for use, unless they are required to be glazed, in which case they are dipped in a glazing composition and again fired. The mode of setting the pieces differs essentially from the Roman method. In manufacture of the tiles called encaustic, in which various designs are pro duced by addition of clays of different colour from that of the ground, the clays first undergo sundry washings and purifications. A portion of the kind which is to form the ground first receives an impression, in the plastic state, from a plaster in relief. The bulk of the tile is made up 