*Project Gutenberg*. Public domain.

654. *Q.*—What is the diameter and
pitch of the screw propeller?

*A.*—The diameter is 7 feet and the
pitch 14 feet. The propeller is Holm’s
conchoidal propeller. Its diameter is smaller
than is advisable, being limited by the draught of
water of the vessel; and the vessel was required to
have a small draught of water to go over a bar.
This engine makes, under favorable circumstances,
100 strokes per minute. The speed of piston with
this number of strokes is 700 feet per minute, and
the engine works steadily at this speed, the shock
and tremor arising from the arrested momentum of the
moving parts being taken away by the counterbalance
applied at the discs.

## LOCOMOTIVE ENGINE.

655. *Q.*—Will you describe the principal
features of a modern locomotive engine?

*A.*—I will take for this purpose
the locomotive Snake, constructed by John V. Gooch
for the London and South Western Railway, as an example
of a modern locomotive of good construction, adapted
for the narrow gauge. The length of the wheel
base of this engine is 12 feet 8-1/2 inches. There
are two cylinders, each 14-1/4 inches diameter and
21 inches stroke. The total weight of the engine
is 19 tons; and this weight is so distributed on the
wheels as to throw 8 tons on the leading wheels, 6
tons on the driving wheels, and 5 tons on the hind
wheels. The engine is made with outside cylinders,
and the cylinders are raised somewhat out of the horizontal
line to enable them better to clear the leading wheels.

656. *Q.*—What are the dimensions
of the boiler?