300
THE NEW ZEALAND GAZETTE.
[No. 7

Put a little water into a large flask, fit with stopper and glass and rubber tubes; boil water and drive off air, closing rubber tube with clip. Let flask cool; weigh; admit air and weigh again. (Put clip into scale with flask). Weigh flask full of air. Fill it with gas from gas-jet and weigh again. (Keep it away from a flame.) Warm flask with air; close with clip. Let flask cool; weigh. Admit air; weigh again.

Take a U tube (two straight tubes joined by rubber tube will do). Pour in water. Hold at different angles; note level of water. For one branch of U tube substitute tube of a glass filter; pour in water; note level in funnel of filter and in tube.

Construct model to illustrate artesian well; also model with branches to illustrate a high-pressure water-supply system.

Very slightly oil wooden cube; float it in water. Measure depth immersed, and total depth of cube. Find the fraction, depth immersed, total depth, and compare with relative density of wood.

Float oil on water; warm water (coloured) on cold water, &c.

Take U tube as before. Pour in mercury. Pour alcohol into one branch, and water into the other until mercury is at same level in both branches. Measure heights of alcohol and water above mercury; find the fraction height of water / height of alcohol; compare this fraction with relative density of alcohol. Repeat for other liquids (including mercury).

Take a U tube, one end closed; hold it with closed end down, and nearly fill with mercury; raise closed end. What happens?

Take the U tube; hold closed end up. What happens? Attach rubber to open end, placing it below surface of water; lower the other end. What comes out?

Make barometer; graduate it. Keep record of readings.

Fill a wide-mouthed bottle with water, and invert it over water; lower a similar inverted bottle, apparently empty, into water; turn it round gradually with its mouth below that of the first bottle. What happens?

Fill a common syringe with water, noting what happens as it is filling with water; hold the nozzle against a piece of sheet rubber or against the finger; try to push the piston down.

Repeat the same experiment when the syringe has only air in it. Is air compressible? Test the same fact with the U tube with air in the closed end, pouring additional mercury into the open end. Try this also with water instead of air in the closed end.

Fit a piece of cardboard or glass plate to the mouth of a glass jar or tumbler; fill the jar with water, and invert it, holding the cardboard against the mouth of the jar. What happens? Repeat the experiment, but only half-fill the jar. What happens? (Invert it over a basin or bucket.)

Substitute a lamp-glass for the jar, fitting a card or plate to both ends. Repeat the experiment. Remove the top plate. What happens? Why?

Make a siphon (the open U tube, inverted, will do). Make a siphon of rubber tube only. Try the effect of raising the free end above the level of the water.

Make a hole at the highest point. What happens? Why?

Take two pieces of rubber cord, one stouter than the other, and two boards. Fasten each cord by a drawing-pin through its end to a board, and tie a loop of silk thread round the cord 12 in. from the drawing-pin. Attach a weight to the loop of one cord, and measure the stretched length. What stretches the cord? Remove the weight; take hold of the cord by the loop, and pull it horizontally until it is stretched to the same extent. What is the force of your pull?

Attach the same weight to the second cord, and repeat the experiments. Place both boards horizontally and connect the loops by a piece of silk; pull the boards apart until the first cord is stretched as much as it was at first. How much is the second cord stretched? What stretches each cord? (After a few experiments fresh pieces of rubber cord should be used.)

Attach a toy wagon to one of the cords. Incline the board at any angle, the fixed end of the rubber cord being at the highest part of the board. Put shot or weights into the wagon until the cord is stretched as much as it was before. What is the total weight of the wagon and shot? Call this the weight. What is the pull on the rubber cord? Call this the power.

Find the fraction or ratio, weight / power.

Measure the length of the inclined plane or board; measure the height of the raised end. Find the ratio or fraction, length / height. Compare it with the ratio, weight / power.