The only requisites which he demands are that something in his line be needed, and that the money is forthcoming to defray the expense, and the thing will be done.  But the railroad he is asked to construct must be necessary, and the necessity must be plainly shown, or no funds will be advanced; and although the theory does not invariably hold good, especially when a craze for railroad building is raging, as a rule no expense for the construction of a road will be incurred without a prospect of remuneration.

Hence the need of railroad communication has caused lines to be constructed through districts where only a few years ago the thing would have been deemed impossible.  The Pacific roads of this country were a necessity long before their construction, and in the face of difficulties almost insuperable were carried to successful completion.  So, also, of the railroads in the Andes of South America.  The famous road from Callao through the heart of Peru is one of the highest mountain roads in the world, as well as of the most difficult construction.  The grades are often of 300 feet and more to the mile, and when the mountains were reached so great were the difficulties the engineers were forced to confront that in some places laborers were lowered from cliffs by ropes in order that, with toil and difficulty, they might carve a foothold in order to begin the cutting for the roadway.

In some sections tunnels are more numerous than open cuts, and so far as the road has gone sixty-one tunnels, great and small, have been constructed, aggregating over 20,000 feet in length.  The road attains a height of 15,000 feet above the level of the sea, and at the highest point of the track is about as high as the topmost peak of Mont Blanc.  It pierces the range above it by a tunnel 3,847 feet long.  The stern necessities of business compelled the construction of this road, otherwise it never would have been begun.

The tunnels of the Andes, however, do not bear comparison with the tunnels, bridges, and snow sheds of the Union Pacific, nor do even these compare with the vast undertakings in the Alps—­three great tunnels of nine to eleven miles in length, which have been prepared for the transit of travelers and freight.  The requirements of business necessitated the piercing of the Alps, and as soon as the necessity was shown, funds in abundance were forthcoming for the enterprise.

But tunneling a mountain is a different thing from climbing it.  Many years ago the attention of inventors was directed to the practicability of constructing a railroad up the side of a mountain on grades which, to an ordinary engine, were quite impossible.  The improvements in locomotives twenty-five and thirty years ago rendered them capable of climbing grades which, in the early days of railroad engineering, were deemed out of the question.  The improvements proved a serious stumbling block in the way of the inventors, who found that an ordinary locomotive was able to climb a much steeper grade than was commonly supposed.  The first railroads were laid almost level, but it was soon discovered that a grade of a few feet to the mile was no impediment to progress, and gradually the grade was steepened.