Minerals and curiosities, for United States department and revenue stamps, and foreign postage stamps. GEORGE E. WELLS, P. O. Box 466, New York City. * * * * * Ten foreign stamps, for fifty postmarks (no duplicates). ANNE H. WILSON, Clermont, Columbia Co., N. Y. * * * * * Stamps. CHARLIE E. WHEELER, Chesterville, Franklin Co., Me. [_For other exchanges, see third page of cover._] * * * * * P. C. H.--In most book establishments the printing is done from stereotype or electrotype plates, taken from the type pages. In the first process one or more pages are placed in an iron frame, and from these a mould is taken in plaster of Paris. Type-metal--a composition mainly of lead and antimony--is poured into this mould, forming a cast of the face of the type. These casts, or "plates," are planed down upon the back to a regular thickness, and from them the printing is made precisely as from the types themselves. In electrotyping, a mould of beeswax, coated with black-lead to give it a metallic surface, is forced by a powerful pressure upon a page of type, producing a perfect fac-simile. After receiving another coating of black-lead, the mould is placed in a tank filled with a solution of sulphate of copper, into which enter the poles of a galvanic or electric battery, the mould being connected with the positive pole, the negative pole being attached to a plate of copper. In an instant a thin film of copper appears on the "black-leaded" surface of the mould. This increases in quantity until it has acquired the thickness of a sheet of stout paper. The upper surface of this "shell," when taken from the mould, is a perfect fac-simile of the face of the original page. This thin shell would be crushed flat by the immense pressure of the printing-press. It must be "backed up" with type-metal. This metal will not, even when melted, adhere firmly to a sheet of copper, but it will adhere to tin, and melted tin will adhere to copper. A sheet of tin-foil is laid upon the back of the copper shell, which is secured in a shallow iron tray, and heated. Melted type-metal is then poured over the plate, filling up every depression, and forming a solid backing, firmly soldered to the shell. The plates are then shaved down to the proper size, and are ready for the press. * * * * *