Atlantic Monthly | Page 4

on the other, whether to pass is required a bridge or a
tunnel, we find either or both designed and built in a manner which
cannot be bettered. He is well aware that the directors like rather to see
short columns of figures on their treasurer's books than to read records
of great mechanical triumphs in their engineer's reports.
Of the whole expense of building a railroad, where the country is to any
considerable degree broken, the reduction of the natural surface to the
required form for the road, that is, the earthwork, or, otherwise, the
excavation and embankment, amounts to from thirty to seventy per cent.
of the whole cost. Here, then, is certainly an important element on
which the engineer is to show his ability; let us look a little at it, even at
the risk of being dry.
It is by no means necessary to reduce the natural surface of the country
to a level or horizontal line; if it were so, there would be an end to all
railroads, except on some of the Western prairies. This was not,
however, at first known; indeed, those who were second to understand
the matter denied the possibility of moving a locomotive even on a
level by applying power to the wheels, because, it was said, the wheels
would slip round on the smooth iron rail and the engine remain at rest.
But lo! when the experiment was tried, it was found that the wheel not
only had sufficient bite or adhesion upon the rail to prevent slipping

and give a forward motion to the engine, but that a number of cars
might be attached and also moved.
This point gained, the objectors advanced a step, but again came to a
stand, and said, "If you can move a train on a level, that is all, --you
can't go up hill." But trial proved that easy inclines (called grades)
could be surmounted,--say, rising ten feet for each mile in length.
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 motion was obtained by the balance of

momentum and resistance, --whence a fall great enough to produce this
regular speed would be advantageous, but no more. On the other hand,
the extra power required to draw the train up the grades much
overbalances the gain by gravity in going down.
Here, then, we have the two extremes: first, spending more money than
the expected traffic will warrant, to cut down hills and fill up valleys;
and second, introducing grades so steep that the amount of traffic does
not authorize the use of engines heavy enough to work them.
The direction of the traffic, to a certain extent, determines the rate and
direction of the inclines. Thus, the Reading Railroad, from Philadelphia
up the Schuylkill to Reading, and thence to Pottsville, is employed
entirely in the transport of coal from the Lehigh coal-fields to
tide-water in Philadelphia; and it is a very economically operated road,
considering