ion of rubbing surfaces,
the friction depends mainly on the nature of lubricant;
oil forced out of bearings, if the pressure exceeds 800
lbs. per square inch longitudinal section;
water a good lubricant if the surfaces are large enough.
Lubrication of engine bearings.

McNaught's indicator.
Main beam, strength proper for.
Main centre, description of,
strength proper for.
Main links, description of,
strength proper for.
Mandrels, expanding, for tubing boilers.
Manhole door.
Manhole of locomotives.
Marine flue boilers, proportions of.
_See_ also Boilers.
Marine boilers of modern construction, proper proportions of.
Marine engines. _See_ Steam Engines, marine.
Mastic cement for setting marine boilers.
Maudslay, Messrs., boilers of "Retribution" and "Great Western," by,
Mechanical powers,
misconceptions respecting.
Mechanical power, definition of,
indestructible and eternal;
the sun the source of mechanical power.
Metallic packing for pistons.
Metallic packing for stuffing boxes.
Meyer, expansion valve by.
Miller, Ravenhill & Co.'s mode of fixing piston rod to piston.
Modern locomotives.
Momentum, or _vis viva_.
Morin, experiments on friction by.
Mudholes of locomotives.
Muntz's metal, composition of.

"Niger" and "Basilisk," trials of.
"Nile," boilers of the, by Boulton and Watt.
Notch of eccentric should be fitted with brass bush.

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 fl