In the early period of railways in this country, when they were built chiefly to promote local interests, and the movement of either freight or passengers over long distances was a comparatively small portion of the traffic, it was customary for all roads to do their business in their own cars, transferring any freight destined to a station on a connecting road at the junction or point of interchange of the two roads. While this system had the advantage of keeping at home the equipment of each road, it resulted in a very slow movement of the freight. As the volume of traffic grew, and the interchange of commodities between distant points increased, this slow movement became more and more vexatious. Soon the railway companies found it necessary to allow their cars to run through to the destination of the freight without transfer, or they would be deprived of the business by more enterprising rivals. So that to-day a very large proportion of the freight business of the country is done without transfer; the same car taking the load from the initial point direct to destination. The result of this is, however, that a considerable share of all the business of any railway is done in cars belonging to other companies, for which mileage has to be paid; while, in turn, the cars of any one company may be scattered all over the country from Maine to California, Winnipeg to Mexico. The problem that constantly confronts the general superintendent of a railway is, how to improve the time of through freight, thereby improving the service and increasing the earnings of the company; and, at the same time, how to secure the prompt movement of cars belonging to the company, getting them home from other roads, and reducing as far as possible upon his own line the use of foreign cars, and the consequent payment of mileage therefor. By common consent the mileage for the use of all eight-wheel freight cars has been fixed at three-quarters of a cent per mile run; four-wheel cars being rated at one-half this amount, or three-eighths of a cent. This amount would at first sight appear to be insignificant, yet in the aggregate it comes to a very considerable sum. In the case of some of the more important roads in the country, even those possessing a large equipment, the balance against them for mileage alone often amounts to nearly half a million annually. It becomes therefore of the first importance to reduce to a minimum the use of foreign cars, thereby reducing the mileage balance; at the same time avoiding any action that will interfere with or impede in any way the prompt movement of traffic.