CHAPTER XXXIX.

=THE MECHANICAL POWERS.=

=Power= 405 =Lever= 405 The principles of 405 Wheels and pulleys considered as levers 405, 406 Power transmitted by gear wheels and pulleys combined 407 =Horse Power= 407 Calculating the horse power of an engine 407 Testing the horse power of an engine 408 =Safety Valve Calculations= 409 =Heat= 410 Latent heat 410 =Water= 410 =Steam= 410 Saturated 410 Superheated 410 Expansion of 411 Absolute pressure of 411 Weight of 411 Volume and pressure of 411 =Heat= 411 Conversion of heat into work 411 Joule's equivalent 411 Mechanical equivalent of heat 411 Mariotte's law 411 Radiation of heat 412 Conduction of heat 412 Convection of heat 412