The enormous train service on some of these first-rank lines demands 353 the highest efficiency in the signalling and interlocking arrangements, and the use of any devices which will ensure increased facility and safety in the working of the traffic. With a crowd of trains passing a signal-cabin in both directions, and often over four lines of way, it is quite possible for a signalman to make a mistake which cannot be rectified in time to prevent an accident. To obtain increased security many railways have adopted the lock and block system previously described, or some adaptation of the same principle, and this method of working will go on extending as the traffic increases. These additional appliances entail additional care and inspection, for although automatical machinery may be exempt from the human frailty of preoccupation of mind or forgetfulness, it is somewhat delicate in its organization, and requires constant supervision to maintain its efficiency. On many of the large lines, much has been done to give improved carriage accommodation. Carriages have been made longer, easier on the road, loftier, better furnished, and better lighted; but there is still a very great deficiency in those conveniences so essentially necessary, especially on trains running long distances without stopping. Drawing-room cars and dining-room cars are no doubt attractive, and may contribute considerably to the popularity of certain routes; but it is questionable whether many of the lines at home and abroad which have adopted such luxuries, have not in doing so commenced at the wrong end, and whether it would not have been more to the public satisfaction to have begun by first providing those conveniences which are found in every carriage on every line in the United States. It is satisfactory to find that there is a steadily growing tendency to so construct passenger carriages that their occupants may, by passages or corridors, communicate with all parts of the same carriage or with the adjoining carriages; and there is every reason to assume that the carriage of the future, either by legislation or consent, will combine both the items of conveniences and intercommunication, and will confer not only greater comfort to the passengers, but also increased protection against those outrages which, unfortunately, too frequently occur under the system of isolated compartments. It will be instructive to watch the results of the passenger receipts 354 on those lines where only first and third-class carriages are used. The elimination of the second class may at first sight appear an innovation; but if there is not any pecuniary loss sustained, there must be a gain in the reduction of unoccupied seats to be hauled. It is customary to provide in every train a liberal number of spare seats of each class to meet contingencies; and the omission of one class may mean the saving of two or three carriages--a very important item in locomotive power.