CHAPTER II

HOW WORK IS DONE

Primitive man's use of the lever, p. 29--The use of the lever as conceived by Archimedes, p. 21--Wheels and pulleys, p. 32--Other means of transmitting power, p. 35--Inclined planes and derricks, p. 37--The steam-scoop, p. 38--Friction, p. 39--Available sources of energy, p. 41.