Popular Science Monthly/Volume 37/July 1890/Apparatus-Making in Education




BY way of further illustrating the truth of what Prof. Woodhull says in his article, Home-made Apparatus, in the August, 1889, number of The Popular Science Monthly, allow me to present some work that has been done here in that direction.

We have no workshop and no tools. Our method of work is this: In the study of natural philosophy, when a principle is being enunciated, some half-dozen or more members of the class are asked to make the piece of apparatus which illustrates this principle. A week is allowed for its completion, or a longer time, if the work involves much difficulty, or if the pupil has much work in other classes. He is allowed to use any material he can get, and he may ask the aid of a blacksmith, carpenter, or any mechanic. But the work, when brought in, must be neatly finished, and must be made of materials that cost absolutely nothing. Of the six or more pieces of the same kind, the neatest and most accurate one is preserved in school. In this way, in the course of time, some hundreds of pieces of apparatus are made which serve perfectly well to illustrate the principles of natural philosophy. These pieces are handled, tested, and compared by the pupils in the class-rooms, and in this way they voluntarily spend spare minutes before and after school hours. They consist of such articles as inertia apparatus, steelyard, balance of equal arms, pulleys, inclined planes, wheel and axle, hydrometer, siphon, fountains, Leyden jar, pith-ball electroscope, gold-leaf electroscope, batteries of various kinds, magnets, electro-magnets, telegraph apparatus, etc. These, if purchased from an instrument dealer, would amount to several hundred dollars.

For materials for construction of apparatus, the pupils ask at home or at stores or shops where they are acquainted. There are always bottles, tin-foil, corks, wax, wood, scraps of wire, iron, tin-plate, bits of thread, cloth, etc., to be had for the asking. Almost every kind of business in some way contributes its share. There is no difficulty whatever in getting these things, for the merchants and mechanics are usually pleased when the boys ask for them.

One of the pieces of apparatus made in class was a steelyard, which was constructed of a foot-rule. Exactly one inch from the end a hole was bored; through this a wire was passed and bent into a loop. This served for the pivot. Three fourths of an inch from the same end another wire, similarly bent and inserted, served for the suspension of the weight. The pea was made of a small piece of pig-iron picked up at the furnace. It was carefully weighed, and had a small cord tied around it so that it could be slid along the beam of the steelyard. This apparatus was made to illustrate the lever of the first order, and when tested weighed as accurately as the grocer's scales.

Another piece was a balance of equal arms, which was sensitive to five milligrammes, either loaded or empty. It is represented in Fig. 1. The beam, support, pointer, and index were cut out of wood. The scale-pans were tin-box tops. The knife-edges

PSM V37 D360 Balance of equal arms.jpg

Fig. 1.—Balance of Equal Arms.

were made of old umbrella wire tempered hard. The weights, from ten grammes to five milligrammes, were made of pieces of copper wire. In making this balance, the pupil had his attention forcibly called, by repeated failures, to the necessity of having the arms exactly equal, to the best position of the center of gravity of the balance, and to the importance of the knife-edges. This balance—the best of four brought in—was used to determine the specific gravities of minerals, and the results obtained agreed closely with those given in Dana's Manual. It was also used in the candle experiment to show that there is gain in weight when a candle burns, and for numerous other experiments.

A hydrometer, made by another boy in the same class, according to a suggestion found in Gage's Elements of Physics, illustrated well the advantage of requiring pupils to make apparatus, even when free access is had to that made by the instrument-maker. A piece of wood cut from the spoke of an old wheel was loaded at one end with lead, so as to make it stand upright. It was immersed in rain-water, and the water-level on it marked 1,000. By means of a Baumæ's hydrometer the level of 900 was found, and distances, equal to the distance between the two marks, laid off above and below. Much to the boy's surprise, the hydrometer thus graduated would by no means coincide with his PSM V37 D361 Hydrometer.jpgFig. 2.—Hydrometer. Baumé. He attributed the error to the absorption of the fluids by the wood, and set to work to make another, taking care this time to rub the wood with beeswax, to render it impervious to liquids; but his second graduation was hardly more satisfactory than the first. He then put on a piece of cork for a float, the wood having failed to keep an upright position in all liquids, and graduated his hydrometer by means of different liquids whose densities had been found with the Baumæ hydrometer, and at last discovered that the divisions were not equal. This piece of work, represented in Fig. 2, consumed all the boy's afternoons for a week; but I saw the effect of it in increased carefulness, and consequently greater accuracy in his subsequent work, and, what was still more important, in increased thoughtfulness.

A condenser for use in distilling water was made after the pattern of Liebig's. The outside tube was made by boring a round piece of wood, ten inches long and two inches in diameter, through with an inch auger. The inside tube, and those for entrance of cold water and exit of hot water, were made of reeds. A bottle served for the still, and the whole was supported on a neat wooden stand.

Such work undoubtedly requires much energy on the part of the teacher, for his suggestions will be needed and asked for many times during the week. But if he is a mere college or high-school graduate who has gained his knowledge of science from the lectures and experiments of the professor, he will find this work of making home-made apparatus even more beneficial to himself than it is to the pupils. He will by means of it have much light thrown upon obscure places, and will accordingly teach more effectively. He will become so familiar with, his work that he will find himself being transformed from a mere hearer of lessons from the book into an enthusiastic co-worker with his pupils.