At the very dawn of art moist clay was molded into useful plates and bowls. This foreran not only all that the potter has since accomplished, but all that has been achieved in the foundry and the mint. In making bricks, tiles, and terra cotta, the first task is to make the clay plastic, then advantage is taken of its plasticity. In like manner we heat a metal to fluidity, and then pour it into a mold to make a fence rail, a stove plate, or a car wheel. An electric bath refines upon this process. Copper, let us say, dissolves in a tank, and concurrently its particles are deposited on a mold from which the metal can be readily stripped, avoiding the distortion inevitable when heat has come into play. Within the past ten years concrete has grown into much importance as a building material, especially as reinforced with steel. It is a great deal easier and cheaper to pour a wall into molds than to lay courses of brick, or cut and dispose stone-work. Elsewhere in this book a few pages are given to reinforced concrete, and its applications. Pressing and Stamping. Pressing, like molding, has of late years much extended its range of forms. In germ it goes back to the distant day when seals were impressed upon clay tablets, and coins or medals were struck from hard matrices. In glass manufacture the press has been used for centuries. Cheap pressed tumblers and bowls have long been accompanied by cheap metal pots and pans, plates and basins, stamped by machinery. To-day much enlarged and improved, such machinery, as a Bliss press, makes a kitchen sink from a sheet of steel, forms gears and pinions from round bars of metal, and executes the intricate curves of a mandolin in a plate of aluminum. For a good while the spinning lathe gave us from thin metallic sheets a variety of cups, saucers, dishes, parts of kettles, lamps, and the like. To-day each of these articles is produced by a single blow of a die, proving that metals are plastic in a degree unsuspected in former days. Thus it comes about that the seams necessary to the tinman and the coppersmith, with all their liability to leaks and uncleanliness, have been largely dismissed and may soon be wholly banished. Pressing is illustrated on pages 184 to 186 of this book. Old and New Means of Conferring Form.