CHAPTER XIII.

GENERAL ECONOMY OF STEAM POWER.

Mechanical efficacy of steam -- proportional to the quantity of water evaporated, and to the fuel consumed. -- Independent of the pressure. -- Its mechanical efficacy by condensation alone. -- By condensation and expansion combined -- by direct pressure and expansion -- by direct pressure and condensation -- by direct pressure, condensation, and expansion. -- The power of engines. -- The duty of engines. -- Meaning of horse power. -- To compute the power of an engine. -- Of the power of boilers. -- The structure of the grate-bars. -- Quantity of water and steam room. -- Fire surface and flue surface. -- Dimensions of steam pipes. -- Velocity of piston. -- Economy of fuel. -- Cornish duty reports. 277