The body of clay which has been described is best developed at Woodbridge and Perth Amboy, and is practically inexhaustible, and although its presence has been known for nearly, if not quite, two centuries, its employment for the production of architectural terra-cotta is of but very recent years.

It is conveniently situated between the large and wealthy cities of New York and Philadelphia, and being contiguous to the seaboard, and in easy communication by rail with all the developing cities of the country, this section should become to us what the Staffordshire district is to England.

The largest terra-cotta works in this country are located at Perth Amboy in New Jersey. Woodbridge and Perth Amboy both owe their prosperity to manufactures of terracotta, fire-brick, and tiles, and the traveller journeying westward in New Jersey, from either of these thrifty towns, will find his way skirted by frequent hollows and excavations, stretching irregularly on either hand.

The color of the rich clay, denuded of the soil and often exposed, varies in shade from a light cream-color, almost white, to a soft buff, and sometimes the clay will be of a dark red color, owing to the abundant presence of the oxide of iron, a very light trace of which impregnates all the clay in the circumjacent region.

The red clays containing oxide of iron in abundance are used only when it is desired to give the terra-cotta a deep red brick color, which is sometimes done for friezes, panels, tiles and other architectural requirements.

For a long distance the way between Woodbridge, Perth

Amboy, and New Brunswick is marked by many of the excavations that have been noted, and which are sometimes of great depth. From the bottom of these, winding wagon roads lead through banks of clay in which large gangs of laborers are regularly at work digging material to be used in the production of terra-cotta and fire-brick, and removing that which is unsuitable for these purposes.

The surface of the country is undulating, and it is but thinly settled, and often a heavy growth of birches, maples, and young pines spreads over it, giving no indications of the riches it conceals, for underlying it is one vast bed of terra-cotta clay, which for fineness of texture and plasticity has no equal in the world.

In applying the term plasticity to this clay, I do not mean it in the common acceptance of that term; but in addition to the quality of receiving and giving form, that also of retaining it, not only while it is being moulded, but in that most trying time to all clays, which is the period that it is yielding its chemical water and "going through the sweat."

It may not be generally known that all things made of moulded clay, although they may appear to be perfectly dry when they go into the kiln, again become softer and almost as plastic as they were when first moulded, and it is this stage of burning that is so destructive to form in the production of artistic and architectural terra-cotta. In describing this critical period in burning, I have used the common parlance of the laborers employed about kilns, for two reasons, the first being that there is no technical term applicable to the same condition of things, and the second is that "going through

the sweat" is a most accurate and literal description. Should the adobes or sun-dried bricks of Egypt, which have been exposed to the influences of that moisture-extracting climate for more than three thousand years, be placed in a kiln and burned, the result would be the same, they would "go through the sweat" and become soft and plastic before they were burned into hard bricks.

The mechanical water has been extracted from them, but the chemical water contained in the clay has never been driven out by burning. The adobe before burning could be soaked in water and in a few hours it would be just as plastic as it was when first made, thousands of years ago, but after burning its plasticity is forever lost.

The vitrifying ingredients usually added to the terra-cotta clays are pure white sand, old pottery, and fire-bricks finely pulverized, and clay previously burned, termed "grog;" these are employed in various proportions, sometimes amounting to nearly thirty per cent. of the mass.

The alkaline salts contained in the clays yield an efflorescence, which, acting upon the silicates of the surface, vitrify to a greater degree the exterior of the terra-cotta, and this harder face should remain intact, and under no avoidable circumstances be allowed to be chipped, chiselled, or broken.

Having prepared the mixture of clays and other ingre dients, it is reduced to the consistency of flour, the pans in the mills are either stationary or revolving; but the latter are much preferable, as they usually do more and better work.

Subsequently, careful pugging or tempering is necessary, so as to thoroughly incorporate and mix the combination of

clays and added ingredients. Hot water is sometimes used in tempering the mass; but a jet of steam injected into the interior of the clay cylinder, about the centre between top and outlet, during the process of grinding is a great aid to the clay.

A one-half inch pipe will answer in most cases, and the quantity of steam injected can be regulated at some convenient point by a suitable valve.

Moulding.

The clay, after being brought to the desired consistency, is formed in a mould, usually in several parts, the clay being pressed into them by the hand, and as soon as one section is finished another is added, and so the moulding of intricate pieces of terra-cotta progresses.

The making of moulds for terra-cotta, when the design is intricate, is a matter of great nicety, and requires careful fitting of the parts, which is not always easy, from the shrinking of the parts not being the same.

The making of the moulds is generally one of the chief delays in the manufacture of terra-cotta for buildings; these moulds cannot be changed at will, nor can alterations be made in the ornaments as the work proceeds, not only because the moulds cannot be changed, but because the pieces cannot be cut without ruining the design. The first work of the architect, after his plans are accepted, should be the preparation of all the details for the terra-cotta portion, as each piece has its place and no other will fill it in the build

ing in that position for which it was designed. There can be none of that hurry and hasty preparation of details now so common on both sides of the Atlantic; there must be carefully matured working details for this material, the manner of joining the parts can best be left to the modeller, who can use locked, rebated, or flanged joints, as may be

best.

The production of objects in terra-cotta from models and reproduction from casts are chiefly mechanical, but oftentimes call for experience and skill. A great difficulty is often presented in taking many good forms from one plaster cast, as the cast is liable to deteriorate.

There are several ways for overcoming this; but that which was largely employed in reproducing some of the most difficult terra-cotta work in the great Albert Hall and other large works in England, is the best.

In this process the plaster cast is covered with grease or soap, and then protected by a rubber cloth, on the top of which modelling clay is placed to the depth of four or five inches and fully covering the surface of the cast, then against the modelling clay a backing of plaster is built, in two or more parts as may be desired, and makes the backing to the mould.

When sufficiently hard the backing of plaster is removed and the rubber cloth and modelling clay taken out and laid to one side, the backing of plaster being again replaced. There will now be an interval between the face of the model and the plaster wall equal to the thickness of the clay removed, which is filled with liquid gelatine.