degree of comparative perfection they are, of course, still in their earlier stage of development. In use, however, they have not been found open to the practical objections urged against them. At first much too complicated and expensive, requiring more machinery than could by any reasonable exertions be kept in order and more care than they were worth, they have now been simplified until a single battery properly located can do all the necessary work for a road of indefinite length. As a system they are effective and do not lead to accidents; nor are they any more subject than telegraph wires to derangement from atmospheric causes. When any disturbance does take place, until it can be overcome it amounts simply to a general signal for operating the road with extreme caution. But with railroads, as everywhere else in life, it is the normal condition of affairs for which provision must be made, while the dangers incident to exceptional circumstances must be met by exceptional precautions. As long as things are in their normal state, that is, probably, during nineteen days out of twenty, the electric signals have now through several years of constant trial proved themselves a reliable safeguard. It can hardly admit of doubt that in the near future they will be both further perfected and generally adopted. CHAPTER XVIII. INTERLOCKING. In their management of switches, especially at points of railroad convergence where a heavy traffic is concentrated and the passage of trains or movement of cars and locomotives is unceasing, the English are immeasurably in advance of the Americans; and, indeed, of all other people. In fact, in this respect the American managers have shown themselves slow to learn, and have evinced an indisposition to adopt labor-saving appliances which, considering their usual quickness of discernment in that regard, is at first sight inexplicable. Having always been accustomed to the old and simple methods, just so long as they can through those methods handle their traffic with a bearable degree of inconvenience and expense, they will continue to do so. That their present method is most extravagant, just as extravagant as it would be to rent two houses or to run two steam engines where one, if properly used, could be made to suffice, admits of demonstration;--but the waste is not on the surface, and the necessity for economy is not imperative. The difference of conditions and the difference in results may be made very obvious by a comparison. Take, for instance, London and Boston--the Cannon street station in the one and the Beach street station in the other. The concentration of traffic at London is so great that it becomes necessary to utilize every foot of ground devoted to railroad purposes to the utmost possible extent. Not only must it be packed with tracks, but those tracks must never be idle. The incessant train movement at Cannon street has already been referred to as probably the most extraordinary and confusing