The invention of stereotyping is also a great improvement in printing. Almost all works, after being put in type, are stereotyped; the advantage is that a new edition can be struck off as often as called for, without the labor of resetting the type. The process of stereotyping differs from common printing, in that the letters, after being set up, are cast in plates of entire pages, from plaster of Paris moulds. The workman in the picture is about removing the moulds from the type beneath. The mould, forming a perfect _fac simile_ of the page intended to be printed, is placed with others in a great oven, where it is dried and baked hard. The edge of the oven can be seen at the right of the picture on the following page, which represents the interior of the Stereotype Foundery. [Illustration: Moulding in Plaster.] While the plaster mould is baking in the oven, the foundery man is getting things in readiness for converting it into lead. Upon the left, in the picture, is a high pile of bars of lead, looking like an irregular chimney. When the bars of lead are put into the cauldron to melt, a certain amount of antimony is put in also, to render it brittle, and tin is added to give a brightness of surface. When the lead, antimony, and tin are well melted, and the scum has been removed, the composition is poured into iron moulds, where it hardens, and comes out in the shape of the lead that was put into the kettle in the first place. These bars of composition, lead being by far the largest material, are put into the boiler over which you see the man working, and melted again, making a molten mass, which is kept liquid by the hot fire beneath and the frequent stirring. When the plaster pages, or moulds, are well baked in the oven, they are ready to be plunged in their lead bath. An iron pan about two feet long, a foot broad, and two or three inches deep, is the vessel, in which is laid a false bottom of iron, called a floater; on this are laid the plaster moulds, face down, and the whole is covered with an iron slab, which does not, however, rest on the plaster moulds, but upon the edge of the iron pan. An iron handle, like that of a basket, is secured to the middle of the pan upon the wooden stand in front of the picture. A crane overhangs the boiler, and from it drops a hook surrounded by four legs; the hook takes hold of the hole in the handle, and the four legs press upon the iron cover of the pan; the crane swings round, holds the iron pan with its plaster moulds snugly shut up in it, and suspends the body over molten lead, lowering it until it is partly sunken in the lead but not wholly plunged in it.