and Marine Boilers.

Incrustation and Corrosion of Boilers.

Locomotive Boilers.

CHAP. VIII.--CONSTRUCTIVE DETAILS OF ENGINES.

Pumping Engines.

Various forms of Marine Engines.

Cylinders, Pistons, and Valves.

Air Pump and Condenser.

Pumps, Cocks, and Pipes.

Details of the Screw and Screw Shaft.

Details of the Paddles and Paddle Shaft.

The Locomotive Engine.

CHAP. IX.--STEAM NAVIGATION.

Resistance of Vessels in Water.

Experiments on the Resistance of Vessels.

Influence of the size of Vessels upon their Speed.

Structure and Operation of Paddle Wheels.

Configuration and Action of the Screw.

Comparative Advantages of Paddle and Screw Vessels.

Comparative Advantages of different kinds of Screws.

Proportions of Screws.

Screw Vessels with full and auxiliary Power.

Screw and Paddles combined.

CHAP. X.--EXAMPLES OF ENGINES OF RECENT CONSTRUCTION.

Oscillating Paddle Engines.

Direct acting Screw Engine.

Locomotive Engine.

CHAP. XI.--ON VARIOUS FORMS AND APPLICATIONS OF THE STEAM ENGINE.

Governor.

Donkey Pumps.

Portable Steam Engines.

Stationary Engines.

Steam Fire Engines.

Steam Excavator.

CHAP. XII.--MANUFACTURE AND MANAGEMENT OF STEAM ENGINES.

Construction of Engines.

Erection of Engines.

Management of Marine Boilers.

Management of Marine Engines.

Management of Locomotives.

MECHANICAL PRINCIPLES OF THE STEAM ENGINE.

CLASSIFICATION OF ENGINES.

1. _Q._--What is meant by a vacuum?

_A._--A vacuum means an empty space; a space in which there is neither
water nor air, nor anything else that we know of.

2. _Q._--Wherein does a high pressure differ from a low pressure engine?

_A._--In a high pressure engine the steam, after having pushed the piston
to the end of the stroke, escapes into the atmosphere, and the impelling
force is therefore that due to the difference between the pressure of the
steam and the pressure of the atmosphere. In the condensing engine the
steam, after having pressed the piston to the end of the stroke, passes
into the condenser, in which a vacuum is maintained, and the impelling
force is that due to the difference between the pressure of the steam above
the piston, and the pressure of the vacuum beneath it, which is nothing;
or, in other words, you have then the whole pressure of the steam urging
the piston, consisting of the pressure shown by the safety-valve on the
boiler, and the pre