The objectors take another step, but again put down their heavy
square-toed foot, and say, "There! aren't you satisfied? you can go
over grades of twenty feet per mile, but no more,--so don't try."
And here English engineers stop,--twenty feet being considered a
pretty stiff grade. Meanwhile, the American engineers Whistler and
Latrobe, the one dealing with the Berkshire mountains in
Massachusetts, the other with the Alleghanies in Virginia, find that
not only are grades of ten and of twenty feet admissible, but, where
Nature requires it, inclines of forty, sixty, eighty, and even one
hundred feet per mile,--it being only remembered, the while, that
just as the steepness of the grade is augmented, the power must be
increased. This discovery, when properly used, is of immense
advantage; but in the hands of those who do not understand the nice
relation which exists between the mechanical and the financial
elements of the question, as governed by the speed and weight of
trains, and by the funds at the company's disposal, is very liable
to be a great injury to the prospects of a road, or even its ruin.

It was urged at one time, that the best road would have the grades
undulating from one end to the other,--so that the momentum acquired
in one descent would carry the train almost over the succeeding
ascent; and that very little steam-power would be needed. This idea
would have place, at least to a certain extent, if the whole
momentum was allowed to accumulate during the descent; but even
supposing there would be no danger from acquiring so great a speed,
a mechanical difficulty was brought to light at once, namely, that
the resistance of the atmosphere to the motion of the train
increased nearly, if not quite, as the square of the speed; so that
after the train on the descent acquired a certain speed, a regular