That waiting charge, the traffic-man explains, is known in the parlance of his business as "demurrage"; and it is another keen example of the constant use to which a railroad puts its equipment, of the tremendous economy that is beginning to be practised in the modern science of railroading. You are introduced to the car-service man, bend low over his desk as he explains a bit of his work to you. Here, for example, is a car filled with automobiles bound from Detroit to a dealer in Worcester, Mass. This car, in a train of some 60 others, leaves Detroit east-bound over the Michigan Central Railroad. At Buffalo it is switched to the tracks of the New York Central & Hudson River Railroad. On the evening of the second day it arrives at Rensselaer, across the Hudson River from Albany, and is given over to the Boston & Albany Railroad. To make a concrete instance, let us see how the B. & A. handles the thing through its car-service department. That department swings into quick action automatically, as soon as the car strikes B. & A. rails at Rensselaer. The freight agent there makes a note of the car and its contents from the way-bill which accompanies it; makes special note, perhaps, of the fact that it is a car designed particularly for the transportation of automobiles. Now let us presume that this big box-car is owned by the Michigan Central. The Boston & Albany will pay that owner railroad 35 cents a day rental--"_per diem_," in the phraseology of the railroads--for the time it is upon B. & A. rails. There are at that very time perhaps hundreds of B. & A. cars on the Michigan Central, and at the end of 30 days these accounts and many, many others are sent to the auditor's department, where they are balanced between the roads with the general freight and passenger accounts. This movement of freight cars makes a valuable barometer of the general condition of business. The daily papers have a custom of making national compilations of car-service reports part of their most interesting market news. In dull seasons the cars come home from long service on other roads. But in very busy seasons all roads have little compunction about borrowing "foreign" cars for use in their local service. With shippers begging cars from every quarter and threatening all manner of dire things, 35 cents daily is a small rental to pay for the use of a roomy car. Besides, the other fellows are all doing the same thing, and no one road can hope to get all its cars back even with the use of a vigilant corps of young men who search "foreign" yards. But in the dull seasons they come trundling home, like lost cattle finding the big barn once again. In the business depression of 1907, a Western car-service man received cars that had been absent from the home road for seven years.