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

CHAP. IX.] INVENTION OF THE STEAM BLAST. 93
presented to the fire being comparatively small, sufficient steam
could not be raised to enable it to accomplish more on an average
than about three miles an hour. The result was any thing but
decisive ; and the locomotive might have been condemned as
useless, had not Mr. Stephenson at this juncture applied the
steam blast, and at once more than doubled the power of the
engine.
Although Trevethick, in the engine constructed by. him in
1804, allowed the waste steam to escape into the chimney, there
was no object in the arrangement except to get rid of a nuisance
and to avoid the unsightliness of the escape steam blowing off in
jets into the open air. The exit pipe adopted by Mr. Trevethick,
as we have already observed, was not contrived with the view
of producing any effect ; nor does any seem to have been pro-
duced, for it is certain that he afterwards abandoned the ar-
rangement. It is remarkable that a man so ingenious as Treve-
thick should not have discerned its advantages ; but it is clear
that he could not have done so, for as late as 1815, after George
Stephenson had discovered and successfully adopted the steam
blast, Trevethick took out a patent, the principal object of which
was to " produce a current of air in the manner of a winnowing
machine, to blow the fire." " Flat plates or leaves," revolving
in a case, were the means adopted by him for this purpose ;
and
in the same patent he proposed to " place in the flue a screw or
set of vanes, somewhat similar to a smoke-jack," which were
" to revolve by connection with the steam-engine, for the purpose
of creating an artificial draught in the chimney." This contrivance
was, however, a useless one, as Mr. Stephenson's mode
of applying the blast already threw it far into the shade as a
means of stimulating combustion by artificial means.
It is remarkable how little Trevethick really accomplished
for railway progress, notwithstanding his ingenuity and skill as
an inventor and mechanician. Instructed by Murdoch and as-
sisted by Vivian, he was enabled to erect his first steam car-
riage, after which he constructed his first railway locomotive.
But Trevethick was one of those men who are satisfied with
making a beginning. He was not endowed with the gift of
continuance— ^the quality of perseverance. With half the clev-