Show pupils how to make a magnet by winding a piece of insulated wire around a nail and joining the ends of the wire to the battery. Make a horse-shoe magnet by bending the nail and winding the wire about both ends in opposite directions.
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.
INCLINED PLANE.--If a plank twelve inches long has one end on the ground and the other on a cart four inches high, one man can roll up the plank the same weight that would require three men to lift, but he has to move the object three times as far.
PROBLEMS
1. Why is a long-handled spade easier to dig with than a short-handled one?
2. Which is easier, to dig when the spade is thrust full length or half length into the earth?
3. Can a small boy "teeter" on a board against a big boy? How?
4. In helping to move a wagon, why grasp the wheel near its rim?
5. In making a balance, why should the arms be equal? In a balance with unequal arms, compare the weights used with the article weighed.
6. In using shears, is it better to place the object you wish to cut near the handles or near the points?
7. Where is the best place to put the load on a wheel-barrow?
8. Notice how three horses are hitched to a plough or binder.
9. Where would you grasp the pump-handle when you wish to pump (1) easily, (2) quickly?
10. Stretch out your arm and see whether you can hold as heavy a weight on your hand as on your elbow.
11. Count the pulleys used in a hay-fork and determine the use of each.
12. If a ton of hay is unloaded at five equal forkfuls, what weight has the horse to draw at each load?
13. Count the cogs on the wheels of a fanning-mill, washing-machine, apple-parer, or egg-beater, and determine how the direction or rate of the motion is changed thereby.
14. Measure the diameter of the large fly-wheel of a thrashing-machine engine, and of that which turns the cylinder in the separator. Decide how many times the cylinder revolves for one turn of the fly-wheel.
15. Think of all the uses of a wedge. Draw one. Compare the axe, knife, and chisel with the wedge.
16. How are heavy logs loaded on a sleigh or truck? How are barrels of salt and sugar loaded and unloaded?
17. There are two hills of the same height. One has a gradual slope, the other a steep one. Which is easier to climb? In what case is it farthest to the top?
18. Why does a cow or horse take a zigzag path when climbing a steep hill?
CHAPTER XIV
FORM IV
SPRING
METHODS OF IMPROVING HOME AND SCHOOL GROUNDS
The study of plants should lead to an intelligent appreciation of their beauties and a desire to have them growing about. Many of our native trees, shrubs, vines, and herbaceous plants are quite as beautiful as some that are procured at considerable expense from nurserymen. A great work remains to be done in cultivating and popularizing our best native species. Up to this point the pupils have been getting acquainted with them in their own natural habitat; the next step should be to use them in covering up harsh and offensive views about the school and home grounds, in softening and giving restful relief to barren yards and bare walls, to ugly fences and uninteresting walks and driveways.
Begin to plan some simple improvements for the spring. These may be repairing of fences and gates in order to protect the grounds from stray animals, the cleaning up of the yards, the gathering of stones which may be used in making a rockery, the planting of trees along the sides and front of the grounds--a double row of evergreens to overcome a cold northern exposure or to exclude from view disagreeable features, the laying out of a walk or drive with borders, flower beds, or shrubs in little clumps.
Plans of grounds well laid out should be examined and discussed in the school-room. Many ill.u.s.trated magazines give useful suggestions. Plans can be worked out on the black-board with the pupils. It will take years to complete such a plan, but the pupils should have a part in making the plan as well as in carrying it out. The aim should be to encourage the use of simple and inexpensive things obtained in the vicinity, wherewith to produce harmony and pleasing natural effects.
Comfort and utility must be considered as well as beauty and natural design. In the school grounds the outdoor games must also be provided for and sufficient room allowed.
Such efforts on the part of the teacher and pupils, if wisely directed, are sure to meet with the approval of the parents and must call forth the hearty co-operation of the trustees.
It is not well to attempt too much in one year. It is better to do a small amount well than to leave much work in a half-done condition.
MAKING AND CARE OF A LAWN
The soil must be drained and not too much shaded by trees. At first it should be summer fallowed or cultivated every few weeks throughout the summer, to kill the weeds and make it fine and level. A thick seeding of lawn gra.s.s-seed should be sown early the next spring and raked lightly in. All levelling and preparation must have been done the previous season.
Coa.r.s.e gra.s.ses, such as timothy, should not be used on a lawn. Red top and Kentucky blue-gra.s.s in equal parts are best and, if white clover is desired, add about half as much white Dutch clover seed as red top. If the soil has been prepared as above, there is no need to use a foster crop of oats or barley, as is done in seeding down meadows. Roll the lawn after seeding and also after heavy rains as soon as the surface dries. Shortly after the gra.s.s appears, begin to run the lawn-mower over it, so as to cut weeds or native gra.s.ses that may be gaining a foothold.
Watering is dangerous, unless carefully and regularly done during the summer, the evening being the best time. Merely wetting the surface by sprinkling encourages shallow rooting and therefore rapid drying out.
Regular mowing and rolling are more important.