t something else is needed. We shall try to find out what it is.

Watch while I hold these strips of paper over this lighted gas stove
high enough to be out of reach of the flame. What happened to them? They
burst into a flame. What did the paper that I held receive that it did
not get when it was lying on the table? Heat. We shall try a match in
the same way, also some thin shavings. They also burn when they receive
heat from the fire. Then what is another requisite for a fire? _Heat._
Name all of the requisites for a kitchen fire. _Fuel_, _stove_,
_oxygen_, and _heat_.

NOTE.--Just here it is a good thing to impress
the care that is necessary in regard to
gasolene, coal-oil, benzine, etc., or any
substance that burns at a low temperature.
Bring out the fact very clearly that it is the
heat that makes fuel burn, that a flame is not
necessary.

HEAT

Experiments to show on what the amount of heat required depends:

1. Heat together two strips of paper of the same size but of different
thicknesses and observe which burns first.

2. Heat together a strip of very thin paper and a match which is much
thicker than the paper, and observe which burns first.

3. Rub a match vigorously on some surface and observe the result.

Conclusions.--1. The amount of heat required to make fuel burn depends
on:

(1) The thickness of the fuel.

(2) The substance composing the fuel.

2. Some substances burn at a very low temperature.

NOTE.--This will explain the order of laying
the fuel for a fire and the use of a match in
lighting it.

OXYGEN

Experiments to show the means of obtaining oxygen:

1. Light a candle, set the lamp chimney over it and observe the result.

2. Raise the chimney by supporting it on two small pieces of wood. Note
the result.

3. Cover the raised chimney with a piece of cardboard. Note the result.

[Illustration: Experiments to show the necessity for oxygen]

Conclusions.--1. A fresh supply of oxygen is constantly required.

2. Two openings are required to ensure a constant supply of oxygen, one
below the fuel and one above it.

3. Oxygen is obtained from the surrounding air.

4. The passage of air through these openings creates a draught.

It will be necessary next to lead the class to see that the supply of
oxygen can be controlled:

1. By the relation of the openings:

(1) Op