Page:The New International Encyclopædia 1st ed. v. 03.djvu/543

iron, containing a knife-bearing, revolving cen- tral shaft, witii curved arms at the bottom to force the ehiy into the press-box. The molds are sanded, then fed in automatically beneath the press-box. After the molds are filled under pres- sure they are moved forward to a delivery table. StifT-mud machines, as the name implies, treat stiffly tempered clay, which is forced through a die by either a plunger or an auger. The plunger gives bars of clay, of fixed lengths. and the auger a continuous bar or stream, but in either case the bars may lie cut into brick by means of parallel wires; or in the case of the auger machines automatic cutters may be used, and the process made continuous, thus increasing the capacity, and also requiring less power. The auger machines may cut the brick either end-

SIDE-CUTTING MACHINE.

wise or sidewise, the machines and product being known, accordingly, as end-cut or side-cut. The plunger machines are end-cut. The auger machines tend to give the brick a laminated structure, which is objectionable. Some moulding- machines combine a vertical pug-mill (see under the article Clay, paragraph Pug-Mills) , with a revolving arm which fortes the clay down into molds ranged around the edge of a horizon- tal revolving table. Plungers from both above and below compress the clay. Dry-clay machines use a pulverized, screened clay, which is fed from a hopper through canvas tubes or chargers into molds, where the clay is pressed from above and below, somewhat as just descrilied. Brick thus made are very dense, but their particles are not well united. These machines are used chiefly to make front brick. After the bricks are turned nut by the machines it is necessary to dry them before burning. This is done in the open air. in covered sheds, or in heated tunnels, from which they are taken to the kilns. For a description of burning see Kil.xs, and for accounts of the brick industry, both in general and in detail, consult : The several annual issues of The Mineral Indus- try (New York. 18n-2-1000) ; Wheeler, Vitrified Paving Brick (Indianapolis, 1895) ; Davis, I'rac- Heal Treatise on the Manufacture of Bricks, Tiles, and Terra-Cotta (London, 1884).

Archæology of Brick. Throughout antiquity two kinds of brick were used, the crude or sun- dried and the kiln-dried or fired bricks. Brick- making was invented in Babylonia, where nature had provided no other building material, there being no quarries or forests; and if, as is asserted by eminent authorities, the earliest civilization was formed in Babylonia, bricks may be deemed the earliest material used in permanent construction, as well as the basis for the invention of the arch, dome, tunnel, and other methods of vaulting. Buildings made of bricks have been discovered dating long before B.C. 4000. The same processes were followed in Egypt, where, how- ever, the use of brick was not nearly so general, as stone-quarries were abundant. Assyria fol- lowed Baliykmia far more closely, using stone hardly at all, except occasionally for foundations and facings. In the preparation of crude bricks, the clay was first freed of grit, stones, and lumps, then mixed with finely chopped straw, then a fixed proportion of water was added, and finally the mass was kneaded with the feet in shallow basins. This material was then thrown into molds varying in size from 14 to I514 inches square, anil from 2 to 4 inches thick. The Baby- lonians allowed the bricks to dry thoroughly before use, but the Assyrians were satisfied with brief and imperfect desiccation ; for usually it is possible to detect separate courses and even sepa- rate bricks in Babylonian ruins, but in the Assy- rian walls all individuality has been lost through the adhesion of moist surfaces. The kiln-dried bricks were used in much smaller cjuantities, for facing the masses of crude brick so as to preserve them from disin- tegration, especially by water, and for thin and inner walls. These bricks were burned by wood fires in ovens or flare kilns. They also were commonly square, somewhat smaller than the crude brick, about a foot jn length and breadth. Usually, one of their flat sides was stamped with the name and titles of the reigning king, and this side was laid downward. The.se bricks have been the best means of fixing the dates of many temples and palaces in Babylonia and Assyria. Besides the regular-sized burned bricks, others were molded in special shapes and sizes: seg- ments of circles for use in columns; wedge- shaped, for use in arches; triangular, for cor- ners; even convex. Undoubtedly, the Babylo- nians deserve the palm for both quality and vari- ety. The bricks were laid in liquid clay, lime mortar, or bitumen. According to Ilerodotiis. in building the walls of Babylon the clay from the trenches was used for making the bricks, which were then laid in 'Hiot asphalt for cement, and between every thirtieth course of bricks placing mats of woven reeds." (Cf. Genesis xi. H. for the building of the Tower of Babel.) . third form of brick used by Babylonians and Assyrians was the enameled brick, in which the body of the brick was only lightly fired so that the enamel could better penetrate.

We do not associate bricks with the Greeks, yet it is certain that among them crude bricks were in general use, especially in the earliest times. At Troy, Tiryns, and other cities of the Mycenæan Age, such bricks formed the constructive