The steam engine familiarly explained and illustrated; with an historical sketch of its invention and progressive improvement; its applications to navigation and railways; with plain maxims for railway speculators. By the Rev. Dionysius Lardner ... With additions and notes by James Renwick ...

234 THE STEAM ENGINE.
be amply sufficient to supply all that could be required for
any hills which occur upon turnpike roads; but it is not to be
forgotten, that not merely an ample supply of motive power,
but also a strength and weight in the machinery proportionate to the power to be exerted, is indispensably necessary.
The strength and weight necessary to ascend a very steep
hill will be considerably greater than that which is necessary
for a level road, or for hills of moderate inclinations; and it
follows that if we ascend those steep hills by the unaided
power of the locomotive, we must load the engine with all
the weight of machinery requisite for such emergencies,
such additional weight being altogether unnecessary, and
therefore a serious impediment, upon all other parts of the
road, inasmuch as it must exclude an equivalent weight of
goods or passengers, which might otherwise be transported,
and thereby in fact diminish proportionally the efficiency of
the machine. It is right, however, to observe, that this is a
point upon which a difference of opinion is entertained by
persons equally competent to form a judgment, and that some
consider that it is practicable to construct an engine without
inconvenient weight which will ascend all the hills which
occur upon turnpike roads.
However this may be, the difficulty is one which the improved system of roads in England renders of a comparatively trifling nature. If horses were resorted to as the
means of assistance up such hills as the engine would be
incapable of surmounting, such aid would not be requisite
more than twice or thrice upon the mail-coach road between
London and Holyhead; and the same may be said of the
roads connecting the greatest points of interlcourse in the
kingdom. Such hills as the ascent at Pentonville upon
the New Road, the ascent in St. James's Street, the ascent
from Waterloo Place to the County Fire Office, the ascent
at Highgate Archway, present no difficulty whatever. It is
only Old Highgate Hill, and hills of a similar kind, which
would ever require a supply of horses in aid of the engine,