to freeze, but that it
does so soon after.

The night before this experiment the children should set out in the cold
air, tightly corked bottles of water. In the morning they will be found
burst by the expansion.

APPLICATIONS

1. Why did some of the ink-bottles burst in the cold room?

2. Find large stones split up into two or more fragments. Explain.

3. Why is fall-ploughed land so mellow in spring?

4. Why does ice float? Think what would happen if it did not.

5. Explain the heaving of oats, clover, wheat.

6. Do all liquids expand on freezing? Try melted paraffin.

THE THERMOMETER

Besides the ordinary thermometer the school should possess a chemical
thermometer graduated from 0 deg. Fahrenheit to 212 deg.

1. Our sensations vary so much under different circumstances and in
different individuals that they cannot be depended on. Find examples of
this and show the need of a measuring instrument.

2. The pupils can learn, by examination of the common wall instrument,
the parts of the thermometer--tube, bulb, liquid (alcohol or mercury),
and scale.

3. Repeat the experiment for expansion of liquids, showing wherein the
apparatus resembles the thermometer, warm the thermometer bulb and watch
the column rise; cool it and note the fall.

4. Set the bulb of the chemical thermometer in boiling water. The
mercury comes to rest near 212 deg. Bury the bulb in melting snow and
notice that the column falls to 32 deg. Give names for these points.
Explain that a degree is one of the 180 equal parts which lie between
boiling point and freezing-point. Show that 32 deg. below freezing must
be 0 deg., or zero.

5. The uses of thermometers for indoors and outdoors; for dairy, sick
room, incubator, and soils; maximum and minimum. Dairy thermometers
registering 212 deg. Fahrenheit may be obtained; they are cheaper than
chemical thermometers.

EXPANSION OF AIR

Half fill a flask with water and invert it uncorked over water in a
plate. Apply a cloth soaked in boiling water to the part that contains
air. Why does the water leave the flask? Apply cold water. Why does the
water return? Any ordinary bottle may be used in place of the flask, but
it is more liable to crack.

Make an air thermometer. See _The Ontario High School Physics_, page
223, also _Science of Common Life_, page 41. Try to graduate it from the
mercurial thermometer. Have the boys make a stand for it.

_Inferences._--Heated gases rise because they e