Oils for lubrication. See Lubrication. 
Oscillation, centre of. 
Oscillating paddle engine, description of. 
Oscillating engine, advantages of,
  futility of objections to;
  details of cylinder;
  framing;
  condenser;
  air pump;
  trunnions;
  valve and valve casing;
  piston;
  piston rod;
  air pump connecting rod and cross head;
  air pump rod;
  eccentric and eccentric rod;
  valve gear;
  valve sector;
  shaft plummer blocks;
  trunnion plummer blocks;
  feathering paddle wheels;
  packing of trunnions. 
Oscillating engines, how to erect. 
Otis’s excavator. 
Outside and inside cylinder locomotives.

Packing for stuffing box of Watt’s engine. 
Packing of piston of pumping engines, how to accomplish. 
Packing of trunnions. 
Paddle bolts, proper mode of forming. 
Paddle centres. 
Paddle floats. 
Paddle shaft, description of. 
Paddle shaft, details of. 
Paddle shaft plummer blocks of oscillating engines. 
Paddle wheels, details of,
  structure and operation of;
  slip of;
  centre of pressure of;
  rolling circle;
  action of oblique floats;
  rule for proportioning paddle wheels;
  benefits of large floats. 
Paddle wheels, feathering, description of;
  details of. 
Paddles and screw combined. 
Parallel motion, description of,
  how to lay off centres of. 
Pendulum,
  cause of vibrations of;
  relation of vibrations of pendulum to velocity of falling bodies;
  conical pendulum or governor. 
Penn, Messrs., engines of “Great Britain,” by,
  direct acting screw engines by;
  trunk engines by. 
Performance of locomotives. 
Pillars, hollow, strength of,
  law of strength varies with thickness of metal. 
Pipe for receiving screw shaft. 
Pipes of marine engines. 
Piston, description of,
  how to pack with hemp. 
Pistons, metallic packing for. 
Pistons for oscillating engines. 
Pistons, how to fit and finish. 
Pistons of locomotives. 
Piston rod, description of,
  strength proper for. 
Piston rods of locomotives. 
Piston rod of oscillating engine. 
Piston rods of direct acting screw engine. 
Pitch of the screw. 
Pitch, increasing or expanding. 
Pitching motion in locomotives. 
Planometers, or face plates. 
Plummer blocks of shafts and trunnions of oscillating engines. 
Plummer blocks for receiving thrust of screw propeller. 
Plunger of feed pump. 
Portable engine, Hoadley’s. 
Porter’s patent governor. 
Ports of the cylinder, area of. 
Pot-lid valves of air pump. 
Powers, mechanical,
  misconception respecting. 
Power, horses, definition of,
  nominal and actual power;
  power of high pressure engines. 
Power necessary for thrashing and grinding corn, working sugar mills,
    spinning cotton, sawing timber,