young and growing fast, you have so much more surface in proportion to
your weight than when you are grown up, that you lose heat from the
blood in your skin very fast; and unless you are warmly dressed, you
become chilled.

When you are chilled, you are using up, in merely trying to keep
yourself warm, some of the energy that ought to be used for growing
and for working. It has been found out by careful tests that children
who are not warmly dressed, and particularly whose arms and legs are
not warmly covered, do not grow so fast as they ought to, and more
easily catch colds and other infections. So take time to put on your
cap and your coat, if the weather is cold; and, if it is snowy, to
button on leggings over your stockings; and then you can play as hard
as you like, and run through the snow, and keep warm and rosy and
comfortable.

Wool is one of the best stuffs for coats and dresses and stockings and
gloves and caps, not only because it is warm, but also because it is
lighter in weight than anything else you could wear that would be
equally warm, and because it is _porous_; that is, it will let the air
pass through it, and the perspiration from the body escape through it.

Don't wear any clothes so tight that you cannot run and jump and play
and fling your arms and legs about freely, or so fine and stylish that
you are afraid of getting them soiled by romping and tumbling.

It is best to wear fairly heavy, comfortable shoes with good thick
soles; then you will not have to wear rubbers, except when it is
actually pouring rain, or when there is melting snow or slush upon the
ground. Felt, or buckskin, or heavy cloth makes very good "uppers" for