The life of George Stephenson, railway engineer - Lighthouse ...

270 LIFE OF GEORGE STEPHENSON. Ichap. xxm.
conditions as the limit of four-wheeled engines ; nevertheless, the
judges allowed it to run on the same footing as the other engines,
to enable them to ascertain whether its merits entitled it to fa-
vourable consideration. It travelled at the average speed of
about fourteen miles an hour, with its load attached ; but at the
eighth trip the cold-water pump got wrong, and the engine could
proceed no further.
It was determined to award the premium to the successful
engine on the following day, the 14th, on which occasion there
was an unusual assemblage of spectators. The owners of the
" Novelty " pleaded for another trial ; and it was conceded. But
again it broke down. Then Mr. Hackworth requested the op-
portunity for making another trial of his " Sans-pareil." But
the judges had now had enough of failures ; and they declined,
on the ground that not only was the engine above the stipulated
weight, but that it was constructed on a plan which they could
not recommend for adoption by the directors of the Company.
One of the principal practical objections to this locomotive was
the enormous quantity of coke consumed or wasted by it—about
692 lbs. per hour when travelling,—caused by the sharpness of
the steam blast in the chimney,* which blew a large proportion
of the burning coke into the air.
The " Perseverance,'' of Mr. Burstall, was found unable to
move at more than five or six miles an hour ; and it was withdrawn
at an early period from the contest. The " Rocket " was
thus the only engine that had performed, and more than per-
* The importance of the contraction of the blast-pipe at the point of its
opening into the chimney, was greatly overrated by Mr. Haokworth. The
contraction of the pipe, in many of the best locomotives, is quite unnecessary,
and indeed rather disadvantageous than otherwise ; for, since the speed of the
engines has been increased, the velocity of the eduction steam is quite sufficient
to produce the needful rarefaction in the chimney, without any ooniJaotion
whatever. In the early locomotives, when the speed of the piston was slow,
the contraction was undoubtedly advantageous; but now that the boilers have
been increased in size, and the heating surface thereby gi'eatly extended, a
considerably less intense blast is required. The orifices of the blast-pipes in
many engines running at the present day are as large as the steam-ports ; consequently
they cannot be said to be contracted at all. In fact, the gi'eater apparent
efficiency of the steam blast, as at present used, is entirely owing to the
greater velocity of the piston.