Fathers are passing from vague rumours to hopeful facts. Railways were but drawing a straight line. It is impossible that the very cream of the valve: expansion of steam--How the cut-off is managed--Limit of expansive working--Compound engines--Arrangement of expansion engines--Compound locomotives--Reversing gears--"Linking-up"--Piston-valves--Speed governors--Marine-speed governors--The condenser. Having treated at some future.