3I shall first treat of bricks, and the earth of which they ought to be made. Gravelly, pebbly, and sandy clay are unfit for that purpose; for if made of either of these sorts of earth, they are not only too ponderous, but walls built of them, when exposed to the rain, moulder away, and are soon decomposed, and the straw, also, with which they are mixed, will not sufficiently bind the earth together, because of its rough quality. They should be made of earth of a red or white chalky, or a strong sandy nature. These sorts of earth are ductile and cohesive, and not being heavy, bricks made of them are more easily handled in carrying up the work.
2The proper seasons for brick-making are the spring and autumn, because they then dry more equably. Those made in the summer solstice are defective, because the heat of the sun soon imparts to their external surfaces an appearance of sufficient dryness, whilst the internal parts of them are in a very different state; hence, when thoroughly dry, they shrink and break those parts which were dry in the first instance; and thus broken, their strength is gone. Those are best that have been made at least two years; for in a period less than that they will not dry thoroughly. When plastering is laid and set hard on bricks which are not perfectly dry, the bricks, which will naturally shrink, and consequently occupy a less space than the plastering, will thus leave the latter to stand of itself. From its being extremely thin, and not capable of supporting itself, it soon breaks to pieces; and in its failure sometimes involves even that of the wall. It is not, therefore, without reason that the inhabitants of Utica allow no bricks to be used in their buildings which are not at least five years old, and also approved by a magistrate.
3There are three sorts of bricks; the first is that which the Greeks call Didoron (διδῶρον), being the sort we use; that is, one foot long, and half a foot wide. The two other sorts are used in Grecian buildings; one is called Pentadoron, the other Tetradoron. By the word Doron the Greeks mean a palm, because the word δῶρον signifies a gift which can be borne in the palm of the hand. That sort, therefore, which is five palms each way is called Pentadoron; that of four palms, Tetradoron. The former of these two sorts is used in public buildings, the latter in private.
4Each sort has half bricks made to suit it; so that when a wall is executed, the course on one of the faces of the wall shews sides of whole bricks, the other face of half bricks; and being worked to the line on each face, the bricks on each bed bond alternately over the course below. Besides the pleasant varied appearance which this method gives, it affords additional strength, by the middle of a brick, on a rising course, falling over the vertical joints of the course thereunder. The bricks of Calentum in Spain, Marseilles in France, and Pitane in Asia, are, when wrought and dried, specifically lighter than water, and hence swim thereon. This must arise from the porosity of the earth whereof they are made; the air contained in the pores, to which the water cannot penetrate, giving them a buoyant property. Earth of this sort being, therefore, of such a light and thin quality, and impervious to water, be a lump thereof of whatever size, it swims naturally like pumice-stone. Bricks of this sort are of great use for building purposes; for they are neither heavy nor liable to be injured by the rain.