If a blanket is thrown upon a burning stick of wood, the wood soon ceases
to burn. The wood stops burning because the oxygen of the air is excluded
from it. _The act of burning,_ i.e. _combustion, is the union of
any substance with oxygen, with the result that heat and light are
produced._ We have learned that a fuel cannot unite with oxygen until
heated to a certain temperature. And, no matter how hot it is, the fuel
will not burn unless it unites with oxygen. Oxygen, then, is the third
requisite for combustion.

The necessity for a draft, _i.e._ a continuous supply of fresh air
which furnishes oxygen, is shown by Experiments 3 and 4.

SAUTED [Footnote 4: To saute is to brown in a small quantity of fat.]
SUMMER SQUASH [Footnote 5: See footnote 3.]

Wash summer squash. Cut it in slices 3/4 inch thick. (Do not remove the
skin or the seeds.) Dip each slice in flour. In a frying pan put some fat
and heat it. Add the squash and cook each slice on both sides until golden
brown in color. Sprinkle with salt and pepper. Then place a cover over the
frying pan and continue to cook the squash until it is tender. Serve at
once.

BAKED WINTER SQUASH [Footnote 6: See "Note to Teacher," Footnote 3]

Wash a squash and cut or split it into pieces of suitable size for
serving. Remove the seeds from each piece and make several gashes (at
right angles to one another) cutting through the pulp down to the shell.
Place the pieces (shell down) on the grating in the oven and bake (at
moderate temperature) until the pulp is tender. Serve hot, with butter,