Modeling materials

Usage examples of clays.

Reading beds, mottled clays and sands, repose upon the Chalk at Woburn, Barnham, Fulmer and Denham, and these are in turn covered by the London Clay, which is exposed on the slopes about Stoke Common and Iver.

Everybody who visited the Clays was taken to see some draft or other of his amorphous and wandering book.

It was not that he did not wish further contact with the world in general, and the Clays in particular.

These ordinary brick clays vary considerably in composition, and many clays, as they are found in nature, are unsuitable for brickmaking without the addition of some other kind of clay or sand.

All clays contain more or less free silica in the form of sand, and usually a small percentage of undecomposed felspar.

The actions of the alkalis and of increased temperature are probably closely related, for in either case the clay is brought nearer to its fusion point, and ferruginous clays generally become darker in colour as they approach to fusion.

It is impossible to give a typical composition for such clays, as the percentages of the different constituents vary through such wide ranges.

All clays are greatly improved by being turned over and exposed to the weather, or by standing for some months in a wet condition.

England the natural deposits of these clays have been largely exhausted.

In other districts, where clays containing limestone are used, the marl is mixed with water on a wash-pan and the resulting creamy fluid passed through coarse sieves on to a drying-bed.

If necessary, coarse sand is added to the clay in the wash-pan, and such addition is often advisable because the washed clays are generally very fine in grain.

The machines used in the preparation of such clays are grinding-mills and pug-mills.

The introduction of machinery greatly helped the brickmaking industry in opening up new sources of supply of raw material in the shales and hardened clays of the sedimentary deposits of the older geologic formations, and, with the extended use of continuous firing plants, it has led to the establishment of large concerns where everything is co-ordinated for the production of enormous quantities of bricks at a minimum cost.

Thick deposits of plateau gravel cover most of the high ground in the southern corner of the county, while much of the northern part is obscured by glacial clays and gravels.

Sey, my boy, there are no Colonel Clays, and no arch Madame Picardets!