fast train is run.

When the conductor pulled the cord at the rear end of the long train a
whistling signal was thus given in the engine-cab, and the engineer,
after glancing down the tracks to see that the signals indicated a clear
track, pulled out the long handle of the throttle, and the great machine
obeyed his will as a docile horse answers a touch on the rein. He opened
the throttle-valve just a little, so that but little steam was admitted
to the cylinders, and the pistons being pushed out slowly, the
driving-wheels revolved slowly and the train started gradually. When the
end of the piston stroke was reached the used steam was expelled into
the smokestack, creating a draught which in turn strengthened the heat
of the fire. With each revolution of the driving-wheels, each
cylinder--there is one on each side of every locomotive--blew its steamy
breath into the stack twice. This kept the fire glowing and made the
chou-chou sound that everybody knows and every baby imitates.

As the train gathered speed the engineer pulled the throttle open wider
and wider, the puffs in the short, stubby stack grew more and more
frequent, and the rattle and roar of the iron horse increased.

Down in the pit of the engine-cab the fireman, a great shovel in his
hands, stood ready to feed the ravenous fires. Every minute or two he
pulled the chain and yanked the furnace door open to throw in the
coal, shutting the door again after each shovelful, to keep the fire
hot.

[Illustration: "FIRING" A FAST LOCOMOTIVE An operation that is
practically continuous during a fast trip.]