The entire problem of bridges is so intricate a phase of American railroad construction as to demand attention in a subsequent chapter. In actual railroad practice it is apt to demand a separate branch of engineering skill, both in construction and in maintenance. We turn our attention back to the main problem of the building of our railroad. When all plans are finished, contracts remain to be divided and sub-divided; for it would be a brave contractor, indeed, who in these days would consent to essay himself, any considerable length of railroad line. In fact, in recent work of heavy nature, the price is almost invariably placed at an indefinite figure, a certain definite percentage of profit being allowed the contractor on each cubic yard of rock or soil. In such a case the contractor's business becomes far less a game of chance; he is, in effect, the railroad's agent supervising its construction at a certain set stipend. Let us say that the construction on our railroad begins in the early spring. As a matter of real fact it would not be halted long because of adverse weather conditions. Even up in the frozen and uninhabitable wilds of the Canadian Northwest, work has been prosecuted on the new Grand Trunk Pacific throughout the entire twelve months. But in summer the construction gangs rejoice. The great proposition of bringing mile after mile of future railroad to sub-grade--the level upon which the cross-ties are to be set--fairly sweeps forward under the genial warmth of the sun. The construction is under the supervision of competent engineers, who are, of course, under the direct supervision of the railroad's own organization. Every six to twelve or fifteen miles of new line is divided into sections, better known as residencies, for each is under the eye of its own resident engineer. He reports to the construction engineer, who in turn reports to the chief engineer of the railroad, an officer who reports to no less person than the president of the company. This great force--for each engineer has gathered about him a competent staff of young men as expert with compass, with level, and with transit as were the men who first projected the line--is in the field as quickly as the contractor. They are to see him bring the line to sub-grade; to see him place bridges and culverts, bisect high hills with cuttings, bore tunnels through even higher hills and mountains, span deep valleys with great embankments. To facilitate quick construction the residencies are made numerous; work begins at as many initial points as possible. These points, of course, are situated, where possible, close to water communication or existing railroad lines, in order that material may be brought with the least possible delay and expense. * * * * *