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.