weight of water; a lead weight only .031 as much heat as water.
Flatirons are made of iron because of the relatively high specific
heat of iron. The flatiron heats slowly and cools slowly, and, because
of its high specific heat, not only supplies the laundress with
considerable heat, but eliminates for her the frequent changing of the
flatiron.

18. Water and Weather. About four times as much heat is required to
heat a given quantity of water one degree as to heat an equal quantity
of earth. In summer, when the rocks and the sand along the shore are
burning hot, the ocean and lakes are pleasantly cool, although the
amount of heat present in the water is as great as that present in the
earth. In winter, long after the rocks and sand have given out their
heat and have become cold, the water continues to give out the vast
store of heat accumulated during the summer. This explains why lands
situated on or near large bodies of water usually have less variation
in temperature than inland regions. In the summer the water cools the
region; in the winter, on the contrary, the water heats the region,
and hence extremes of temperature are practically unknown.

19. Sources of Heat. Most of the heat which we enjoy and use we owe
to the sun. The wood which blazes on the hearth, the coal which glows
in the furnace, and the oil which burns in the stove owe their
existence to the sun.

Without the warmth of the sun seeds could not sprout and develop into
the mighty trees which yield firewood. Even coal, which lies buried
thousands of feet below the earth's surface, owes its existence in
part to the sun. Coal is simply buried vegetation,--vegetation which
sprouted and grew under the influence of the sun's warm rays. Ages ago
trees and bushes grew "thick and fast," and the ground was always
covered with a deep layer of decaying vegetable matter. In time some
of this vast supply sank into the moist soil and became covered with
mud. Then rock formed, and the rock pressed down upon the sunken
vegetation. The constant pressure, the moisture in the ground, and
heat affected the underground vegetable mass, and slowly changed it
into coal.

The buried forest and thickets were not all changed into coal. Some
were changed into oil and gas. Decaying animal matter was often mixed
with the vegetable mass. When the mingled animal and vegetable matter
sank into moist earth and came under the influence of pressure, it was
slowly changed into oil a