General view of works of Henry Maurer & Son, taken from Sewaren.

Port Murray.

Fireproofing Company, which has its headquarters at Pittsburgh, and whose original plant in New Jersey was the factory at Port Murray, Warren county, which uses Hudson shale (Pl. XXXIII, Fig. 2). In 1900 this company acquired the Perth Amboy Works, known as the Old Pardee Works; in January, 1901, the fireproofing factory at Lorillard was taken over, and in July, 1901, the Raritan Hollow & Porous-Brick Company at Keasbey. Other factories are those of C. W. Boynton, Sewaren, and one located at Spa Springs, which began in 1869 as the Anness Pottery, and was subsequently known as Anness & Lyle, Staten Island Terra-Cotta Lumber Company, and is now the Staten Island Clay Company.

In addition to the nine factories above mentioned, fireproofing is now manufactured by the Brinkman Terra-Cotta Company, near Piscataway, and by the National Clay Manufacturing Company, of South River, which purchased the old Edgar Brick Works in 1902, and has more or less re-modeled them. Anness & Potter, at Woodbridge, also began the manufacture of fireproofing during 1902, and some hollow brick are made at Crosswicks by John Braislin & Son (Pl. XXXIV, Fig. 2).

The rapid growth of this industry in New Jersey is due to several causes. It is for the most part due to an inexhaustible supply of clay, which in former years had little or no value, and even at the present day would probably not be put to any use other than that for which it is now dug. Furthermore, these clay deposits are in general close to tide water, so that the product can be shipped either by boat or rail to the large eastern markets. Cheap fuel is also an important factor.

CONDUITS.

Clays and manufacture.-Conduits form a line of clay products, the use of which has greatly increased in the last few years. These are hollow blocks of varying length, having sometimes several cross partitions and rounded edges, and are used for pipes for electrical cables and wires below ground. On this account they have to be hard-burned, with dense body, and are salt-glazed.

The clays used are similar to those employed for making fireproofing, although they are somewhat more carefully selected with regard to plasticity and freedom from pyrite and limonite lumps. They must also burn dense at a moderate temperature.

The conduits are molded in auger stiff-mud machines. They are then removed from the cutting table on a pallet, and placed on a stand (Pl. XXXIV, Fig. 1), where the ends are trimmed smooth before the pieces are taken to the drying floor or drying tunnel. In drying the conduits are stood on end. The burning is commonly done in down-draft kilns, between cone 8 and 9, although some manufacturers burn lower than this. The average shrinkage that takes place in a long conduit is about as follows: Length freshly molded, 39 inches; length air dried, 371⁄2 inches; length burned, 35 inches.

New Jersey conduit industry.-There has been a great demand for conduits in the large eastern cities during the last two years, many being used in New York city especially, in the construction of the rapid transit subway, so that the following large plants have been running almost exclusively on this line of work:

The National Fireproofing Company, Standard plant, Perth Amboy;
The National Clay Manufacturing Company, at South River;
The Globe Fireproofing Company, at Clayville.

Conduits are also occasionally made at the fireproofing factories.

Stiff-mud machine for molding conduits. Globe Fireproofing Company, Clayville. Conduit, after molding, is placed on the stand at the left to have its edges trimmed smooth.