tury lenses larger than three and a half inches of the furnace, the enamel becomes vitrified could not be made. At that time a Swiss and incorporated with it. It then passes to clockmaker, Guinand, produced them as the annealing furnace. This process was inlarge as nine inches, of the greatest perfec-vented by Mr. William Cooper, of the firm tion. The secret remained with him for a of Cooper & Belcher, New York, whose exlong time, but was finally, by one of his sons, tensive works at Newark, N. J., supplied imparted to M. Bontemps, who in 1828 pro- 60,000 feet for the New York Crystal Palace. duced lenses of twelve to fourteen inches. Another variety, the flocked, has now come The secret was in keeping the mixture ac- more into use. The process is nearly the tively stirred when liquid, and then suffering same, except that a smooth opaque surface it to cool and anneal in the pot. Lenses are is given to the glass before the enamel is apnow made of flint glass twenty-nine inches plied. in diameter, and weighing two cwt.

Soluble glass has been made of later years of equal parts silica and caustic potash. This is soluble in boiling water, and is used extensively for making buildings and all combustible bodies fire-proof.

In the manufacture of bottles, the metal, on being withdrawn from the melting pot on the end of the blowing tube, is, if for common black bottles, shaped in concavities that are made in the edge of the marver. Fine bottles of flint glass are shaped in moulds of brass or iron, which are made in two parts hinged together, so that they may be opened and shut with the foot. Bottles for champagne, soda water, etc., are made of extraordinary strength, and tested before using by hydraulic pressure. They ought to support, for this purpose, a pressure of 40 atmospheres, or 600 lbs. on the square inch. Notwithstanding the great strength with which they are usually made, the breakage in the manufacture of champagne is rated at 30 per cent.

The production of vessels of colored glass is conducted in a very ingenious manner. The coloring matters are various. Blue transparent glass is made with 2 lbs. oxide of cobalt; azure blue, 4 lbs. oxide of copper; ruby red, 4 ozs. oxide of gold; other colors by various combinations. Sometimes the color is incorporated merely with the outer portion of the glass. This is effected in the blowing by dipping the lump of clear glass, when shaped upon the marver, into the pot of melted colored glass, and then blowing it to the shape required, and flashing out, if desired to convert it into panes. The color may afterward be reduced in depth by grinding, and clear spots reached by grinding through the color. In the process of "casing," a portion of partially blown flint glass is inserted into a thin shell of colored glass, and then blown until it fills the shell, with which it becomes incorporated by heating and further blowing; casings of different colors may be thus applied. The glass is drawn out into tubes in a In painting, the color, mixed with a flux manner that illustrates the curious maniputhat will fuse at a lower temperature than lations of the metal. The workman, with the glass, and with boiled oil, is laid on with his blowing tube, accumulates a certain a brush as in ordinary painting, or by blocks quantity by successive dips into the meltas in calico printing. The glass is then ing pot. This is then blown into a globe. heated, when the flux melts, and sinks into Another workman then takes hold with a the body. The painting of glass for church pontil, at a point exactly opposite the blowwindows was formerly carried to a high de-ing tube. The two men then separate, and gree of excellence, that moderns have not been able to equal. Although the receipts have been preserved in ancient treatises, the process has been lost.

Enamelled glass has of late been much used. The glass of the New York Crystal Palace is an illustration. In this process the enamel substance is ground to an impalpable powder, and then laid with a brush, in a pasty state, upon the glass. After the paste is dried, the ornament is etched out either by hand or by machinery. The glass being then softened in the intense heat

the globe contracts in the middle, which being drawn out to the size of the tube desired, cools, and the hotter portions successively yield to the drawing, until a tube of 100 feet or more hangs between the workmen. The diameter of the bore retains its proportion to the thickness of the glass; hence thin tubes must be drawn from globes blown to a large size. These tubes of colored glass may be converted into beads. Beads have always been a great element in the trade with the North American Indians, being highly prized by them.