CHAPTER IV.

ENERGY.

Energy of motion and of position—Energy can be transformed, not created or destroyed—Not created by free-will—Conservation of mechanical power—Convertibility of heat and work—Nature of heat—The steam-engine—Different forms of energy—Gravity—Molecular energy—Chemical energy—Dynamite—Chemical affinities—Electricity—Produced by friction—By the voltaic battery—Electric currents—Arc light—Induction—Magnetism—The magnetic needle—The electric telegraph—The telephone—Dynamo-electric engine—Accumulator 36