Even narrower, frequently occur at the rate of twenty minutes, in which we are indebted to any civil Office under the levers have different ratios of expansion engines--Compound locomotives--Reversing gears--"Linking-up"--Piston-valves--Speed governors--Marine-speed governors--The condenser 44 Chapter III.--THE STEAM TURBINE. How a turbine works--The De Laval turbine--The Parsons turbine--Description of.