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

CHAP. IX.1 DESCRIPTION OF THE ENGINE. 91
boiler, working the propelling gear with cross heads and connecting
rods. The power of the two cylinders was continued by
means of spurwheels, which communicated the motive power to
the wheels supporting the engine on the rail, instead of, as in
Blenkinsop's engine, to cogwheels which acted on the cogged
rail independent of the four supporting wheels. This adoption
of spur gear was the chief peculiarity of the new engine : it
worked upon what is termed the second motion. The chimney
was of wrought iron, around which was a chamber extending
back to the feed-pumps, for the purpose of heating the water
previous to its injection into the boiler. The engine had no
springs whatever, and was mounted on a wooden frame supported
on four wheels. In order, however, to neutralize as much
as possible the jolts and shocks which such an engine would
necessarily encounter from the obstacles and inequalities of the
then very imperfect plateway, the water-barrel which servedTor
a tender was fixed to the end of a lever and weighted, the other
end of the lever being connected with the frame of the locomotive
carriage. By this means the weight of the two was more
equally distributed, though the contrivance did not by any means
compensate for the total absence of springs.
The wheels of the new locomotive were all smooth,—and it
was the first engine that had been so constructed. From the
first, Mr. Stephenson was convinced that the adhesion between
a smooth wheel and an edgerail would be as efficient as Mr.
Blackett had proved it to be between the wheel and the tram-
road. And, although every one at that time argued that the ad-
hesion upon a tramrail was by no means a criterion of what the ad-
hesion would be upon an edgerail, Mr. Stephenson felt confident
that there was no essential difference between the one and the
other. Before, however, constructing the smooth wheels for his
locomotive, he had the adhesion between the wheels of a car-
riage, properly loaded, and the rails, tested and satisfactorily
proved by experiment. He made a number of workmen mount
upon the wheels of a wagon moderately loaded, resting their
entire weight upon the spokes on one side, and found that the
wagon could thus be easily propelled forward without the wheels
slipping. He then determined to fix smooth wheels upon his "