Machinery, as we commonly understand the term, is not much employed in the manufacture of glass; but chemistry, which saves as much labour as machinery, and performs work which no machinery could accomplish, is very largely employed. The materials of which glass is made are sand, or earth, and vegetable matter, such as kelp or burnt seaweed, which yield alkali. For the finest glass, sand is brought from great distances, even from Australia. These materials are put in a state of fusion by the heat of an immense furnace. It requires a red heat of sixty hours to prepare the material of a common bottle. Nearly all glass, except glass for mirrors, is what is called blown. The machinery is very simple, consisting only of an iron pipe and the lungs of the workman; and the process is perfected in all its stages by great subdivision of labour, producing extreme neatness and quickness in all persons employed in it. For instance, a wine-glass is made thus:--One man (the blower) takes up the proper quantity of glass on his pipe, and blows it to the size wanted for the bowl; then he whirls it round on a reel, and draws out the stalk. Another man (the footer) blows a smaller and thicker ball, sticks it to the end of the stalk of the blower's glass, and breaks his pipe from it. The blower opens that ball, and whirls the whole round till the foot is formed. Then a boy dips a small rod in the glass-pot, and sticks it to the very centre of the foot. The blower, still turning the glass round, takes a bit of iron, wets it in his mouth, and touches the ball at the place where he wishes the mouth of the glass to be. The glass separates, and the boy takes it to the finisher, who turns the mouth of it; and, by a peculiar swing that he gives it round his head, makes it perfectly circular, at the same time that it is so hardened as to be easily snapped from the rod. Lastly, the boy takes it on a forked iron to the annealing furnace, where it is cooled gradually. [Illustration: Glass-cutting.] All these operations require the greatest nicety in the workmen; and would take a long time in the performance, and not be very neatly done after all, if they were all done by one man. But the quickness with which they are done by the division of labour is perfectly wonderful. The cheapness of glass for common use, which cheapness is produced by chemical knowledge and the division of labour, has set the ingenuity of man to work to give greater beauty to glass as an article of luxury. The employment of sharp-grinding wheels, put in motion by a treadle, and used in conjunction with a very nice hand, produces _cut_ glass. Cut glass is now comparatively so cheap, that scarcely a family of the middle ranks is without some beautiful article of this manufacture. [Illustration: Sheet-glass making.]