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 ...

310 TH.E STEAM ENGINE.
ments to simple facts and results, which can neither be denied nor disputed, leaving, for the most part, the inferences
to which they lead to be deduced from them by others.
It may be premised, that persons proposing to engage in
any railroad speculation should obtain first a table of gradients; that is, an account of all the acclivities upon the
line from terminus to terminus, stating how many feet in a
mile each incline rises or falls, and its length. Secondly,
it would also be advantageous to have a statement of the
lengths of the radii of the different curves, as well as the
lengths of the curves themselves. Thirdly, an account of
the actual intercourse which has taken place, for a given
time, upon the turnpike road connecting the proposed termini, stating the number of coaches licensed, and the average
number of passengers they carry; also as near an account of
the transport of merchandise as may be obtained. The latter,
however, is of less moment. An approximate estimate may
be made of the intercourse in passengers, by allowing for
each coach, upon each trip, half its licensed complement of
load. Fourthly, the water communication by canal or
otherwise between the places; and the amount of tonnage
transported by it. With the information thus obtained, the
following succinct maxims will be found useful —
No railroad can be profitably worked without a large intercourse of passengers. Goods, merchandise, agricultural produce, &c. ought to be regarded as of secondary importance.
II.
A probable estimate of the number of passengers to be
expected upon a projected line of railroad may be made by
increasing the average number of passengers for the last
three years, by the common road, in a twofold proportion.