Figure 2 shows a forge made by William E. Tappae. A hand-bellows is mounted on a wooden base about ten by twenty-four inches in size, and is worked by a lever handle supported in a frame twenty-six inches in height. The bellows consists of two boards connected by flexible leather tacked to the edges. The upper board is stationary, and an inch central opening is covered on the inside by a two-inch flap of chamois fastened at one point, forming a valve. As the handle is pushed up, the air rushes in, and when pulled down, the valve closes and the compressed air is forced through the metal nozzle to the glowing coals. The carved-wood anvil was stained black and the other parts were painted a bright vermilion. Figure 3 explains one way of connecting levers, and their uses as a mechanical aid. The base is four by fifteen inches in size, and the pillars are respectively six and ten inches in height, and are firmly mortised and glued into the base. The upper lever is eighteen inches in length, and connects with the ten-inch lower lever. The lead weights, sliding on the narrow edges of the levers, balance each other, and show how the heavy wagon of coal is balanced in the office by the weight on the scale-beam. A wedge made of oak ten inches in height and five inches in width is indicated by Figure 4. Figure 5 represents a diminutive pile-driver, twenty-eight inches in length, showing the plan and action of a large machine. [Illustration: SIMPLE MECHANICAL APPARATUS MADE BY BOYS UNDER 14 YEARS OF AGE. DRAWN BY J. ABDON DONNEGAN. Fig. 1. FURNACE Fig. 2. FORGE Fig. 3. LEVER SCALES Fig. 4. WEDGE Fig. 5. PILE DRIVER Fig. 6. SCREW PRESS Fig. 7. INCLINED RAILWAY] The two-pound drop-hammer falls a distance of twenty-two inches in the grooves of the vertical posts which are mortised and glued into the base, as are also the oblique braces to which are attached the bobbin, or axle, and crank, on which the cord is wound that raises the hammer. This hammer is a flat piece of iron having two pieces of wood, each four by two and one-half inches in size, cemented to it. A wire hook is attached just above, and the extended arm of the hook as the weight nears the top, meets a projecting pin, and slips the weight from the cord. Figure 6 is the model of a wood-press useful in pressing flowers for an herbarium. The base and pressure board are each ten inches square, the supports eight inches in height, and a wooden screw connected with the upper board turns in the cross-piece. This and the models shown in the drawings numbered 3, 5, and 10 were made by Harry Stoecker.