This treatise is the outcome of a continuous personal interest in railroads, practically coincident in point of time with the period of active participation of the Federal government in their affairs. During these years, since 1887 when the Act to Regulate Commerce was passed, as the problem of public regulation has gradually unfolded, opportunity has offered itself to me to view the subject from different angles. At the Massachusetts Institute of Technology, as instructor of embryo engineers in the economic aspects of their callings; in service for the United States Industrial Commission in 1900-01, in touch alike with government officials and, travelling all about the country, with shippers and commercial bodies during a period of acute unrest; and finally ripening the practical experience, thus gained, in the favoring atmosphere of Harvard University, seeking to imbue future citizens with a sense of their civic responsibilities; through all these years, the conviction has steadily grown that, as one of the most fundamental agents in our American economic affairs, the subjection of transportation to public control was a primary need of the time. An earnest effort has been made to set down the facts concerning this highly controversial subject with scientific rigor and with fairness to all three of the great parties concerned, the owners, the shippers and the people. If bias there be, it will in all likelihood be found to favor the welfare of the "dim inarticulate multitude,"--that so inert mass of interests and aspirations, too indefinitely informed as to details and too much occupied in earning its daily bread, to be able to analyze its own vital concerns, to give expression to its will, and even sometimes, as it seems, wisely to choose its spokesmen and representatives. It is this helpless and unorganized general public, always in need of an advocate, which, perhaps, most strongly appeals to the academic mind. If there be lack of judicial poise in this regard, it is, at all events, palliated by free confession in advance.