As an application of the electro-magnet, show pupils how to make a telegraph sounder. (See Manual on _Manual Training_.) If possible, examine the construction of an electric bell. The motor and electric light are other common applications of the current. Take up the uses of the motor in factories, and for running street-cars and automobiles. Show the necessity for a water-wheel or engine to produce the current, and for wires to connect. Explain that batteries are not used to produce large currents, but that machines called dynamos, similar to motors, when driven by steam or water-power, will yield electric currents as batteries do. STEAM The power of steam may be shown by loosely corking a flask and boiling the water in it until the cork is driven out, or by stopping the spout of a boiling tea-kettle, or by letting a stream of steam impinge on a toy paper wheel. Encourage pupils to learn all they can about steam and gasolene engines and their uses. FARM TOOLS This topic should be dealt with only in so far as it can be made a subject for actual observation by the pupils. Children should learn to be thoughtful and observant and to do all kinds of work, manual as well as mental, intelligently. MACHINES (Consult _The Ontario High School Physics_, Chap. IX.) LEVER.--When a _lever_ is used to lift a log, one end is placed under the log, a block called a _fulcrum_ is placed under the lever as close as possible to the log, and then the workman pulls down on the outer end of the lever. For example, if the fulcrum is one foot from the log and ten feet from the man, the latter can raise ten pounds with a pull of one pound, but he has to move his end of the lever ten times as far as the log rises. Try it. See other examples in plough handles, see-saw, balance, scissors, wheel-barrow, pump-handle, handspike, crowbar, canthook, nut-crackers. ROPE AND PULLEY.--In the _rope_ and _pulley_ note that when the pulley is a fixed one, the only advantage is a changed direction of the rope. When the pulley is _movable_, the horse pulling will have only half the weight to draw if the pulley is single, one quarter if double, one sixth if triple, etc. Thus in the case of a common hay-fork the horse draws only half the weight of the hay, but he walks twice as far as the hay moves. COGS.--If one wheel has eighty _cogs_ and the other ten, the latter will turn eight times to the former's once. BELT.--When a _belt_ runs over two wheels, one having, say, one fifth of the diameter of the other, the smaller will revolve five times for one revolution of the other. CRANK.--With a _crank_ two feet long, one may turn a wheel twice as easily as with one one foot long, but the hand will move twice as far. If a wedge is two inches thick at the large end and ten inches long, a man may lift 1000 pounds by striking the wedge a 200-lb. blow.