But this operation--however good the glue may be, or however well the veneer may be pressed down--is not sufficient to cause the veneer to adhere permanently to the foundation, especially at the edges, where the air is liable to enter, and to cause the veneer to rise. To prevent this inconvenience, the veneer, at and near the edges, is kept down, either by the pressure of heavy weights, or, still better, by the action of screw-presses. These screw-presses consist of two pieces of wood or clamps, which are brought to any degree of closeness by means of two wooden screws, each screw passing through holes in both clamps, the handles of the two screws being, respectively to each other, outside the opposite clamps. The clamps are opened, by means of the screws, to such a width as to admit the edge of the veneered wood between them; and the screws are then worked up till the clamps grasp the wood tightly, where they remain till the glue is quite cold, and the veneer closely adhering to the foundation. But even all this care is not in every case sufficient to produce a firm adhesion of the veneer to the foundation. It frequently happens that, when the hardened veneered surface is tried with the hammer, a hollow sound indicates that there is yet a place where the veneer has a vacancy beneath it. In such a case, the only remedy is one of a curious kind--viz., to lay a hot iron on the defective part of the veneer, by which the glue beneath is remelted. A small part of the veneer, reaching from the defective part to the edge, is also similarly heated, and the glue beneath remelted. Then, by means of the veneering hammer, the superfluous glue which had caused the defect is squeezed out, and pressed to the edges of the veneer through the kind of channel which had been prepared for it by the heated iron. Where the surface of the wood to be veneered is more or less cylindrical, such as a pillar, the front of a drawer, &c., the piece of veneer has a curvature given to it, corresponding in some degree to that of the surface on which it is laid, by the action of hot water, before the glueing is effected. By sponging one side of the veneer with hot water, it causes that side to swell, while the other side remains dry; the consequence of which is, that the wetted surface rises into a convex form, leaving the other side hollow or concave:--this is, in fact, an instance of _warping_, where a thin piece of wood is either unequally heated or damped on opposite sides. The hollow side is then laid on the glued foundation. When the veneered surface is dry, its edges are trimmed, and its surface scraped and sand-papered, preparatory to the finishing processes which the piece of furniture is to undergo. Manufacture of Glue.