Pens are sometimes made of other metals besides steel, as brass, or zinc, and sometimes of gold. Those made of gold are, of course, too expensive for general use, but as they are never corroded by the ink, they last a very long time, and can always be cleaned by washing; and as the whole wear is at the point, this is tipped with an alloy which is exceedingly hard. ARTS AND TRADE PROCESSES. WOOD AND PLATE ENGRAVING. Illustration: WOOD ENGRAVING. Engraving consists principally of two kinds, that in which the design is made to project, and that in which it is cut in or indented; the first kind is used in wood engraving, and in engraving metallic or wooden blocks and cylinders for calico printing, the other is called “plate engraving,” and is used to produce copper, steel, and zinc plates for printing. In wood engraving a block of box wood is used, or several pieces are screwed or tongued together in order to make a block of the required size, for the box wood must be cut across the grain, therefore large blocks are not easily procured. These blocks are about an inch in thickness, so that they may range with type and be printed with it, they are made perfectly smooth on the face, which is rubbed with a little flake-white and Bath brick, to give it a whitish and slightly roughened surface. On this prepared surface the design is drawn with a black-lead pencil, and the block is then put into the hands of the engraver, who cuts away--to the depth of about one-twentieth of an inch--all those parts which have not been blackened by the pencil, leaving every line and dot of the drawing projecting, and this serves as a sort of stamp or type, to print from. (See “Printing.”) In this way the illustrations to the present work are produced.