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SECTION II. THE MANUFACTURE OF TERRA-COTTA.

The manufacture of terra-cotta is an important one in France, and the statues and other objects displayed in the Paris exhibitions have been remarkably fine.

In its manufacture in England an important clay has long been the potter's clay of North Devon and Dorsetshire, the analysis of which, by Weston, being as follows:

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Each of these clays contains a small amount of alkalies.

The clays of the coal measures, technically known as the fine-clays," are also much esteemed for this purpose.

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In the north of England and in Scotland, the purest

lumps of fire-clay, selected by their color and texture, are used by themselves in the production of terra-cotta; but the concerns of Mr. Blashfield, of Stamford, and others near London, produce a body of much better texture by a careful and thorough mixture of clays.

It requires greater care, and is slightly more expensive for labor; but these are small considerations in comparison to the increased compact, homogeneous and better vitrified body which results from using a mixture of clays.

The precise combination of clays varies with the appearance desired for the terra-cotta; sometimes it is a light cream, or a soft buff color; at other times it may be a cherry-red, or a hard brownish-red color.

A partial vitrification of the mass is desirable in the production of terra-cotta, as it enhances the durability of the body, and, in order to achieve this, clays like the Dorsetshire are added, the small amount of alkalies which they contain acting as a flux and fusing the body to a harder consistency.

New Jersey produces a great variety of clays, and the belt of country underlaid by them extends entirely across the State, and, as described by the State geologist, includes an area of three hundred and twenty square miles; while the area within which these deposits have been worked to the present time is only about seventy square miles, the actual openings of the clay beds being only a very small fraction of the last-named area.

The average depth of these clay deposits is more than three hundred and fifty feet, and the order of supersession is shown in the following table :

1. Dark colored clay (with beds and laminæ of lignite)

2. Sandy clay, with sand in alternate layers

3. Stoneware clay bed

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These clays are one of the most important elements of the material wealth possessed by the State.

Large quantities of clays are marketed annually for making fire-brick, pottery, terra-cotta ware of all kinds, tiles, retorts, crucibles, facings for wall papers, etc.

The average price per ton is four dollars, and the average aggregate production of fire-clay alone, in its crude state, exceeds one million dollars.

New uses for clay of this character are being developed all the while. The New York Terra-cotta Lumber Company has established large works at Perth Amboy for the manu facture of lumber by mixing resinous sawdust with the wet clay, which is left porous after the burning, by the sawdust being consumed.

The material is thoroughly ground and mixed in a mill, carried to the upper portion of the building by an elevator bucket belt. There it is shovelled into a compressor, through which it passes to the floor below, and is forced through a die into any requisite shape, and remains in that portion of the building for a time, to stiffen. It is then carried to the ground-floor and dried on a brick floor heated by flues running underneath it from a furnace.

It now goes in the form of slabs to the ovens, where it is brought to a great heat, which burns out the sawdust.

This occupies about forty-eight hours, and produces in that period about one hundred and eighty tons of fire-proof lumber.

It is next planed, tongued, grooved, or sawed into any desirable shape, the dust being carried off by a steam blower.

It can be applied to a variety of uses; it is light, bulk for bulk, and may be united like joiners' work or nailed into place like so much wood.

It has been employed very satisfactorily for filters in the waterworks of the Holly system. When immersed in boiling asphalt for a few moments, sufficient bituminous matter is absorbed to resist the action of water, as the asphalt becomes part and parcel of the material and does not flake off when exposed to cold or dampness, as with common brick, solid terra-cotta, or iron.

It is a good insulator, and the cheapness of the material and the ease with which it can be made water-proof may bring it largely into use for underground telegraphy.

In addition to the purposes which have been named, it

can be used for grain and elevator bins, refrigerators, safe and vault linings, fire-proof jackets for iron columns, safety warehouses, shelves and partitions for libraries, under linings for hearths, etc.

In devoting so much space to the description of the New Jersey terra-cotta clays, no slight is intended to the terracotta productions of other sections of this country, as the work done by the Boston Terra-cotta Company and the Lake View Terra-Cotta Company, of Chicago, Ill., is of a high character. They seem to take great care in the execution of all architectural terra-cotta, and have produced a large number of designs for private and public buildings in all portions of the country, with credit to themselves and satisfaction to the architects and owners.

In the States of New York, Ohio, and Illinois there are works for the production of this material, which, although now comparatively small, are certain ere long to develop into large manufactories.

In speaking so highly of the terra-cotta clay of New Jersey, I do not mean to be understood that it is suitable for use without any mixtures or other special preparation, as no terra-cotta clay can be so worked with safety; neither should the terra-cotta clay be confounded with fire-clay, the requirements for which are different, but that of this State is also one of the best in this country, or in the world.

The English, Germans, and French are each in our own van in the production of tasteful and artistically finished terra-cotta; but with a superior clay, and a tendency to develop artistic ideas of finish and form, we shall not long be in the rear.

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