CLAY BRICK.
Brick is a most valuable building material. Its comparative cheapness, the ease with which it is transported and handled, and the facility with which it is worked into structures of any desired form, are its valuable characteristics. It is, when properly made, nearly as strong as the best building stone. It is but slightly affected by changes of temperature or of humidity; and is also lighter than stone.
Bricks are much used in architectural construction, but pro portionally much less in engineering structures, notwithstanding their good qualities which recommend them as substitutes for stone. In former editions of this volume arguments were given why brick under certain conditions should be substituted for stone in engineering structures, particularly as recent improvements in the process of manufacture had decreased the cost while they had increased the quality and the uniformity of the product; but at about the time of the improvements in the quality of brick, the developments in the portland cement industry led to the greatly increased use of concrete in both architectural and engineering construction, and consequently brick is now a relatively less important building material than formerly. Nevertheless brick is still an important constructive
material; and the increasing cost of lumber is likely to increase the importance of brick as a material of architectural construction; but concrete owing to its cheapness and strength is likely to be used more and more in engineering structures where brick formerly was employed.
There are two kinds of clay brick,—fire brick and common brick. Both are made by submitting clay which has been prepared properly and moulded into shape, to a temperature which converts it into a semi-vitrified mass.