XXXIII. MAGNETS AND CURRENTS

XXXIV. HOW ELECTRICITY MAY BE MEASURED

XXXV. HOW ELECTRICITY IS OBTAINED ON A LARGE SCALE


INDEX


GENERAL SCIENCE




CHAPTER I

HEAT


I. Value of Fire. Every day, uncontrolled fire wipes out human
lives and destroys vast amounts of property; every day, fire,
controlled and regulated in stove and furnace, cooks our food and
warms our houses. Fire melts ore and allows of the forging of iron, as
in the blacksmith's shop, and of the fashioning of innumerable objects
serviceable to man. Heated boilers change water into the steam which
drives our engines on land and sea. Heat causes rain and wind, fog and
cloud; heat enables vegetation to grow and thus indirectly provides
our food. Whether heat comes directly from the sun or from artificial