[Because of business changes, it is necessary to state that the air pump referred to in previous articles can be purchased from C. E. Wyeth, Newark, O.]

Exp. 29. Lung Test No. 2.

A very amusing, but none-theless valuable experiment may be made by the use of "C" in Fig. 8 of the Feb. No. Balance "C" carefully by the use of a few small shot or by placing water in "C" until it barely floats. Place in a quart bottle of flat shape and of glass thin enough that the sides of the bottle may be compressed by pressure of the thumb and fingers. When "C" is in the bottle the water should reach the neck of the bottle. Now bend a glass tube, close one end by fusion or otherwise, attach a foot of rubber tubing and pass the glass tube twothirds through a cork. The glass tube and attachments are a "make believe only." Blow into the rubber tube with apparent great effort meantime pressing the sides of the bottle. The diver falls slowly to the bottom because the pressure on the sides of the bottle reduces the capacity of the bottle and this condenses the air volume above

the water. Since liquids transmit pressure equally in all directions the air in "C" is condensed, more water enters the slot in the cork, “C” grows heavier than water and falls to the bottom. Of course "C" rises when the pressure is removed. You may have to try two or three times before you leave just the right volume of air in the bottle. Hold the bottle in your own hands and allow some delicate pupil to "blow down" "C" and refuse to allow some strong "smart" boy to cause it to fall more than half way.

Exp. 30. Atmospheric Pressure Supports a Column of Water.

Secure a glass tube about onehalf inch in diameter and eighteen. inches in length. It may be necessary to smooth the ends by grinding on a common grindstone. Fill a tall jar or other vessel with water, place the tube in water closing the top with thumb and then lift from the water. A partial vacuum is formed above the water in the tube and the fifteen pounds atmospheric pressure supports the water.

Place a small marble or pebble in the vessel and closing the tube with the thumb lower the tube until just over the marble. Remove the thumb and the inrush of the water will carry the marble high up

in the tube. The force of running water rolls stones along the stream beds, the friction rounding off the corners and making the thousands of boulders and pebbles.

Close the tube and insert in water and notice the vibration of the water up and down the tube when the thumb is removed.

Exp. 31. Water Pressure.

Pressure of liquids depends upon depth and area and not upon quantity. Attach 6 or 8 feet of small rubber tubing to a small funnel and at the other end attach a pint bottle the bottom having been removed. Fill the bottle with water and note the "water seeks its level" and rises in the funnel to the level of the water in the bottle.

Now have some one hold the hand over the funnel while the bottle is lifted high in air. The water shows a pressure of many pounds and will burst from the funnel.

Explain to your pupils the philosophy of "stand pipes" in city water works and the use of flumes in mining for gold.

Exp. 32. Why Drops of Water are Round.

Read "Surface Tension" in any Physics or Encyclopaedia and explain by diagram how molecules are attracted toward the center of a drop of falling water. Explain how every liquid surface acts as though covered with an invisible elastic film. Show how a needle

may be floated upon the surface of still water. Do not fail to make the following experiment. Select a bottle having a mouth an inch in diameter and tie over it a piece of common mosquito netting. Fill with water, place the palm of the hand on the mouth of the bottle and invert. Lift the bottle from hand and the water remains in the bottle. Incline the bottle slightly and the unbalanced weight of the water causes it to flow out freely. Surface tension is strong enough between the meshes to prevent the water flowing.

Exp. 33. Volcano for the Geography Class.

For this and succeeding experiments get five cents' worth each of sulphuric acid and pulverized potassium chlorate.

To show your geography classes a fine volcano, mix carefully onehalf of the potassium chlorate with an equal volume of pulverized sugar. Place a small portion of this mixture on a brick or stone and apply a match. Drop one drop of the acid on an equal portion and note how the acid ignites it. Now make a paper tube by wrapping a piece of paper about a foot square around a broom stick. Better tie a string round the tube and close one end of the tube by ramming in paper wads. Place a spoonful of the mixture in tube and drop upon it a drop of the acid. Have your pupils bury the tube

upright in a box of dirt or sand built in imitation of a volcano. A metal tube answers better than the paper one.

Exp. 34. Real Fire Under Water.

Cover with water in a small vaseline bottle or small glass a piece of phosphorus half the size of a pea and a few crystals of potassium chlorate. By means of a glass tube place some of the acid immediately upon the two substances. Bright flashes of fire will be seen in the

water. Hold the thumb over the upper end of glass tube while conveying the acid to the bottom of the vessel. Several drops of acid may be necessary.

This experiment is given to show the wonders of science and create interest in the mind of the pupil.

ELECTRICITY.

Before the air grows too warm and moist, every teacher ought to make some of the simple though beautiful and instructive experiments in electricity. The following experiments are easily made. and illustrate the laws of frictional or static electricity. No cost attaches to the performance of the. experiments.

Exp. 35.

Lay upon a clean dry table, desk or board a 6 by 8 inch piece of cheap tablet paper. Hold firmly with the left hand and stroke sev

Exp. 37. To Test the Kind of Electricity.

Bend a inch L on the end of an 8 inch copper or iron wire or small rod. Hang upon this a loop of tissue paper or better still tinfoil and after inserting wire in a cork suspend in a clean dry bottle. See that the two ends of the loop hang parallel and are about 11 inches long. This apparatus is called an electroscope and is used to detect the presence and kind of electricity. It will be well if you fasten a lead bullet at the top of

the rod. Electrify the glass rod and present to the electroscope. The leaves of the loop spread because they are both charged with the same kind of electricity (+), and like electricities repel. Now present the electrified rubber or sealing wax and the leaves collapse because unlike electricities attract. Charge the electroscope either or, then bring the electrified paper in experiment 35 to the knob to see whether the paper is or Try a varnished ruler or a feather duster for electricity. Note the kind in each

case.

Exp. 38. Electricity Produces Motion.

Suspend in a horizontal position by a thread a light 3 foot ruler. Electrify either the glass or rubber and hold near the end of the ruler. The ruler will follow the electrified object round and round. By holding it alternately above and below the end of the ruler it may be made to rock up and down through a distance of a foot or more. A wood splinter may take the place of the ruler.

Exp. 39.

Make a paper cylinder 2 or 3 inches long and 2 inches in diameter. Electrify the rubber or sealing wax and by holding over the cylinder it may be made to roll

Exp. 41.

Suspend by a silk thread 18 inches long a pith ball size of a small marble. The ball should be carefully rounded and will work better if covered with light tinfoil. Bring near it the electrified ruler or glass and note how it is first attracted, then repelled. What law applies here? When repelled by the glass bring near it the rubber or sealing wax and note effect. What law applies in this case? Suspend two pith balls and note how they repel each other when electrified. Why? The pith balls may be used instead of the electroscope to detect the presence and kind of electricity.

Exp. 42. Struck by Lightning. After rubbing the glass or sealing wax briskly present to the ear or nose. The spark you receive is a genuine stroke of lightning and the report is a clap of thunder.

percent, and by the whitewash he is spreading over you. When he starts out to get a job with his loafer's habits, his musty character, and his 70-percent Diploma, you may continue to set his plate for he will soon come back to board with you. P. Why do you graduate him if he is not worthy?

T. Because he is "smart" and can get 70 percent.

P. When he finishes his High School course, I intend to send him to college, after he earns some money. He will be forced to study there.

T. If you do, remember the 70percent Diploma is the only one he will ever receive. I have never known a pupil that did not study in the evenings while in the High School, to be able to complete even the easiest course in any college. Should you become wealthy and he continue to deceive you, the college may let him hang on for a year or two merely to increase the enrollment.

P. What profession do you think my boy is best adapted to?

T. Whittling. The lower stratum of all the professions is filled with his like and they are all hungry.

P. What should I do with him? T. Make him go to work in school if possible; if not, take him out and let him learn a trade or business. He may make a success of life if you get him out soon

enough and make him go to work. He will not get an education without your assistance even if he is "smart." Many roads lead to success besides the one via scholarship. You imagine he is getting learning. He is not. He is getting habits of idleness.

P. Why don't you teachers make him study?

T. Because you will not help. P. Do you really believe he could succeed in school if I should give the matter proper attention? T. I do.

P. Do you believe a pupil can be compelled to study?

T. I do.

P. About what percent of such pupils do you have?

T. About twenty.

P. I suppose such pupils come from humble homes?

T. Often from the best. Vice makes a target of unprotected culture and refinement. A poisoned mind can not study. High School pupils from lowly homes generally try to prepare themselves for making a living and for good citizenship.

P. How would you select those of your pupils destined to be among the most successful?

T. Find out what ones study in the evenings.

P. Well, do the best you can for my boy as I wish him to teach until he earns enough money to pay his way at a Law College. If he should