It would have been difficult to predict the final outcome had not an entirely new factor appeared, which transformed the conduct of the beef packing industry.[113] Specially constructed stock cars owned by private companies began to be built. These favored the perpetuation of competition between eastern and western packers. To checkmate this, the western packers had already embarked in 1879 upon the ownership of privately owned refrigerator cars for the carriage of their finished products. The custom was adopted by the railways of paying for the use of these cars by making an allowance of so much a mile as a deduction from the established tariffs. This at once opened the way to secret rebates of all sorts. The refrigerator traffic in these private cars was large in volume, very regular and highly concentrated as to source. A large tonnage could be diverted at any time to that road which could best show its appreciation of the favor. The Grand Trunk, for instance, in 1887 swept the board, monopolizing this entire business for a brief time, obtaining it by secret and discriminating rates. The railways, jointly, sought to free themselves from the domination of the large packers; but the phenomenal growth of their business, both domestic and export, rendered them too powerful to resist. According to expert data, during nine months to May 1, 1889, three shippers alone received from one line of road $72,945 for the use of their cars. This about equalled the initial cost of eighty new cars. For the fiscal year 1895, $8,744,000 was paid by the railways of the United States for the use of these cars--about $4,000,000 of this being in the form of rental. At this rate, profits of from twenty-five to fifty per cent. upon the investment accrued to the great packers. These virtual rebates, of course, drove all competitors from the field. The story of the gradual extension of this system of private cars to include fruit and produce business belongs in another place. Suffice it to say that the bondage was broken only by the passage of the Hepburn Act of 1906. The growth of these private refrigerator car lines caused the disappearance of live stock shipments. Packing and slaughtering on a large scale at the seaboard, either for domestic consumption or export, was doomed. Meantime, however, the controversy over the relative rates on beef and cattle continued just as if anything really depended upon it. The issue was again submitted to the commissioner of the Trunk Line Association in 1887. In the following year a select committee of the United States Senate was appointed at the urgent request of the cattle raisers. Testimony before this committee showed in detail how eastern packers were striving to build up establishments near the points of consumption, but were driven out of the business by the relatively high costs of shipping cattle, as compared with the rates at which dressed beef could be actually delivered from Chicago and Missouri river points. This entire history, aside from its significance as a study of personal discrimination, illustrates the effect of a relatively increasing differential rate, partly open and partly secret, against the raw material of an industry as compared with the finished product. The result, at all events, has been to concentrate the packing industry in the Middle West. Nor is the controversy closed even yet.[114] But this time it is a question, not between the seaboard and Chicago, but between Chicago and Missouri river points, or those still nearer the southwestern ranges. Fort Worth and Oklahoma City now become complainants against the Missouri river points.[115] Always and everywhere the manufacture seeks to develop at or near the source of the raw material. Whenever this tendency does not appear in an industry it is pertinent to inquire how far the relative adjustment of rates is responsible for the phenomenon.