Atlantic Monthly

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 th