locomotive. And this will hold good for both hard
and soft-tired wheels.

What then is the advantage, if any, of rubber-tired wheels? The
advantages claimed may be enumerated as follows: increased tractile
power, with a given weight, secured without damage to roadways; ease
of carriage to the supported machinery, whereby it--the machinery--is
saved from stress and wear; and economy of the power, expended in
moving the extra weight required by rigid-tired wheels, to secure the
required frictional resistance. The last-mentioned claim depends upon
the first, and must stand or fall with it. The saving of roadway,
ease of carriage, and its favorable result upon the machinery, are
generally conceded.

A denial of the first claim has been made, by those interested in the
manufacture of rigid-tired traction engines and others, in so far
as the rubber tires are employed on comparatively smooth surfaces;
although the increased tractile power on quite _rough_ pavements and
roads is acknowledged.

This denial is based upon results of experiments performed on the
streets of Rochester, England, between the 9th October and the 2nd
November, 1870, by a committee of the Royal Engineers (British Army),
with a view to determine accurately the point in question.

Care was taken to make the circumstances, under which the trials
took place, exactly alike for both the rubber and the iron tires. The
experiments were performed with an Aveling and Porter six-horse power
road engine, built in the Royal Engineers' establishment. The weight
of the engine, without rubber tires, was 11,225 pounds; with rubber
tires, it weighed 12,025 pounds. Without rubber tires it drew 2.813
times its own weight up a gradient of 1 in 11; with rubber
tires, it drew up the same incline 2.763 times the weight of engine,
with the weight of rubber tires added; showing that, although it drew
a little over 2,200 pounds more than it could do without the rubber
tires, the increase of traction was only that which might be expected
from the additional weight.

It is claimed, moreover, that the additional traction power and
superior ease of carriage on rough roads, secured with rubber tires,
is dearly bought at the very great increase in cost, of an engine
fitted with them, over one not so fitted.

This is a point we regard as not fully settled, though it will not
long remain in doubt. There are enough of both types of wheels now in
use to soon answer practically any qu