A handle turns a series of spur-wheels, which in turn give a rapid motion to a twelve-inch walking-beam. To one end of this walking-beam is attached a piston-rod, with a soft rubber disk working in a brass cylinder five inches long and three and a half inches in diameter. Iron fittings, including two brass valves, one on each side, connect with the cylinder; an air-chamber is formed with a fitting and cap. The suction caused by the upward motion of the piston will draw water from a pail or cup through a rubber tube connected with the end fitting of the right-hand valve, then through the valve to the cylinder; the downward motion of the piston causes the water to pass through the left-hand valve to the receiving vessel, and the air-chamber tends to make the flow regular. Parts of the machine were painted blue and striped with gold bronze.
SIMPLE MECHANICAL APPARATUS MADE BY BOYS UNDER FOURTEEN YEARS OF AGE.—DRAWN BY J. ABDON DONNEGAN.
By the removal of one pane of glass from a window facing south, the apparatus shown in Figure 15 may be used, like a magic lantern, to project transparencies, in a darkened room.
A pine board, fourteen inches square and one inch in thickness, has an opening in the middle to receive a wooden frame seven inches square, holding a six-inch cosmorama lens, having a focus of eighteen inches. A three-inch plano-convex lens having a focus of nine inches, mounted in a wooden frame, slides along a slit or opening in a board hinged to the inner side of the board which is cleated to the window.
A plate-glass mirror, eight by fifteen inches in size, is secured to a board hinged to a wooden rod, which can be turned from the inside, and is raised and lowered by a cord winding on a key. The mirror is lowered and inclined until the sunlight is reflected through the lenses, and then a circle of intense light, from ten to fifteen feet in diameter appears on the wall or screen. Both lenses will not cost more than two dollars, and the apparatus will most impressively illustrate experiments in light and sound.
An easily made electric lamp is shown by Figure 16. An Argand chimney is fastened to a wooden base, with the cement known as "Stratena," and partly filled with water. A cork coated with paraffine is placed inside the chimney, and a rod of carbon twelve inches long and one-sixteenth of an inch in thickness being inserted in the cork, the upward pressure of the water on the cork causes the end of the carbon rod to come in slight contact with a thick rod of carbon which is fastened obliquely to a square piece of wood, cemented near the top of the chimney. A brass chip fastened to the wood keeps the thin rod of carbon in position, and when two copper wires connect the carbons with six to ten jars of a bichromate battery, a light appears where the two carbons meet. As the thin rod wastes away, the cork rises and keeps the end of the rod almost in contact with the other carbon point.
An ambition to creditably make a mechanical contrivance or apparatus is noticeably characteristic of many boys. The construction of an aquarium, a sailboat, or a telescope, or some similar object, is of absorbing interest to such lads; and the making of the electrical apparatus of straws, sealing-wax, etcetera, once described by Professor Tyndall, has merely tasked the ingenuity of thinking boys to improve upon the apparatus.
Many educators maintain that manual training of a pleasant character, adapted to the age of the pupils, should form an essential element in the education of boys and girls, and should be placed on a par with the regular studies. There is no doubt that such instruction stimulates ambition and tends to develop taste, skill, and natural invention. At the same time an insight into mechanical occupations, with some practical experience in the handling of tools, may assist a boy in choosing a calling suited to his taste, and better prepare him to enter some practical industry, if his choice should incline toward such an occupation.