In the other press steam is replaced by compressed air vont:lined in a reservoir. which may be tilled by uaeugns of an nir-compre.sing engine. The bed-plate carrying the molds has a reelmlinear in.d kn. When all all kit! is to be pressed the mold k brought under the presser; by means of suitable valves and pipes air is sent tun cylinder-piston carrying the plunger.
The pressure of the air forces the presser down into the mold, the valves are reversed, and the pisttin and presser fly back. A new mold is now under the plunger. The operation may be repeated as often as desired by simply opening and closing the air-valves. In this press, as in the other. the pieces are forced out of the molds by rising plugs or bottoms. The differ ent motions of this press are entirely automatic, with the exception of operating the air valves. In order to form the air-bubbles which are often seen inside of solid pieces of glass, they have been pressed with cavities on the outside, and after being reheated they are closed by pressing the outside down with suitable tools, thus inclosing the air in the cavities.
Rolling Plate-Glass.—A new method and apparatus for rolling plate and sheet glass has been introduced by Mr. James W. lionta, of Wayne, Pa. The main features of the operation are first, rolling, the glass plate on one side, then placing it between platens, then raising both platens, then rotating the same, then lifting one of said platens, and then rolling the other side of the plate. The machine for accomplishing this work has combined with a presser roller a movable platen for passing the glass underneath this roller, and is vertically sliding frame having journals which carry the second platen. There are special devices for bringing the platens together and locking their journals, and for raising, lowering, and ro tating the locked platens, as well as for releasing the latter with the unrolled side of the glass uppermost, so that it may be ready for the next part of the operation.
Gold-Mill : see Mills, Gold.