520 THE POPULAR SCIENCE MONTHLY. 



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 per- 

 haps 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 illustrat- 

 ing scientific principles than that which has held sway in labora- 

 tories for years. Its great merit lies in its simplicity. The stu- 

 dent's mind is confused by a complex piece of apparatus. He 

 loses sight of the principle which you would teach in his per- 

 plexity to solve the riddle of the machine. Again, this home- 

 made 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 ade- 

 quate 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 prin- 

 ciples 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. Contriv- 

 ances 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. 



