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

CHAP, xn.] INVEHTION OF THE DYNAMOMETER. 137
been started, Trevethick's first engine having been constructed
with this special object. Stephenson's friends having observed
how far behind he had left the original projector of the loco-
motive in its application to railroads, perhaps naturally inferred
that he vrould be equally successful in applying it to the pur-
pose for which Trevethick and Vivian originally intended it.
But the accuracy with which he estimated the resistance to
which loads were exposed on railways, arising from friction and
gravity, led him at a very early stage to reject the idea of ever
successfully applying steam power to common road travelling.
In October, 1818, he made a series of careful experiments, in
conjunction with Mr. Nicholas Wood, on the resistance to which
carriages were exposed on railways, testing the results by means
of a dynamometer of his own construction. His readiness at all
times with a contrivance to enable him to overcome a difficulty,
and his fertility in expedients, were in no respect more strik-
ingly displayed than in the invention of this dynamometer.
Though it was found efficient for the purpose for which it was
contrived, it will not, of course, bear a comparison with other
instruments for a similar purpose that have since been invented.
The series of practical observations made by means of this in-
strument were interesting, as the first systematic attempt to
determine the precise amount of resistance to carriages moving
along railways.* It was thus for the first time ascertained by
experiment that the friction was a constant quantity at all ve-
locities. Although this theory had long before been developed
by Vince and Coulomb, and was well known to scientific men as
an established truth, yet at the time when Mr. Stephenson made
his experiments, the deductions of philosophers on the subject
were neither believed in nor acted upon by practical engineers.
And notwithstanding that the carefully conducted experiments
in question went directly to corroborate the philosophical theo-
ries on the subject, it was a considerable time (so great were the
prejudices then existing) before the conclusions which they
established received the sanction of practical men.
* The experiments are set forth in detail in "A Practical Treatise on Eail-
roads and Interior Communication in General." By Nicholas Wood, Colliery
Viewer, C. E. London: Hurst, Chance, and Co., ed. 1831, pp. 197-253.