Page:Popular Science Monthly Volume 35.djvu/542

520 boards have not the means wherewith to purchase apparatus to any great extent. This fact has led some firms to manufacture what might be called demonstration apparatus, much cheaper and simpler in construction than that hitherto used, and therefore vastly superior for illustrating principles, although not sufficiently refined for making accurate measurements; like a story told for illustration by a public speaker, short and to the point, but not embellished so much as to divert the mind from the argument. This is a step in the right direction, but it does not solve the problem. The apparatus is still so expensive that it will be a long time before school boards will be able to purchase it.

Driven by necessity, therefore, which frequently proves to be the mother of invention, the teacher must seize upon familiar objects which chance to be at hand, and, with slight changes perhaps in their construction, use them as apparatus with which to illustrate the principles of his science. Oftentimes he will find that this simple, home-made apparatus is far better for illustrating scientific principles than that which has held sway in laboratories for years. Its great merit lies in its simplicity. The student's mind is confused by a complex piece of apparatus. He loses sight of the principle which you would teach in his perplexity to solve the riddle of the machine. Again, this homemade apparatus has special merit in the eyes of the school trustee who sees that with an expenditure of five cents something, has been made which usually costs five dollars.

The second great difficulty in the solution of our problem is that school courses, as they are now planned, do not allow adequate time for experimentation. It may seem strange to say that one can make his own apparatus and experiment with it in less time than is required to use the old-fashioned apparatus, and yet we positively and emphatically state this. For example, the principles taught by the so-called "fountain in vacuo" are much more quickly illustrated by a bottle with rubber stopper and tubing, as shown in Gage's "Elements of Physics," page 3, Fig. 3. In this case the lungs are used as an air-pump. If the same bottle and tubing be arranged as shown in the above-mentioned text-book, page 59, Fig. 40, the lungs may be used as a condenser, and the bottle will supply the place of a condensing chamber. Contrivances by which all the experiments may be performed which usually require air-pump and condenser are as simple as those mentioned above. The common-school teacher who has difficulty in securing air-pump and condenser may rejoice in the thought that he has a pair of lungs which may be made to supply the place of both, and are less liable to get out of order. They will not require him to spend his Saturday afternoons in oiling them and fixing valves.