Arguing in still another way: Average number of cars in each passenger train handled in United States is 3.95, of which mail cars amount to 0.43, or 11 per cent. Eleven per cent. of the average earnings of a passenger train is 13.8 cents, but mail contributed only 9.4 cents. That is, it should pay 47 per cent. more than it does to be made to contribute a fair share to the insufficient earnings of a passenger train. Mails are fairly responsible on basis of space used for 11 per cent. of the cost of running a passenger train, or 16.17 cents, and as dead weight per foot of space is greater with mails, their proportion of train mile cost is even larger. They pay little more than one-half this cost. By building larger capacity cars and larger engines, the cost of handling freight traffic, entirely in the control of the carrier, has been reduced to follow rate reductions and increased expenses. On the other hand, because methods of conducting passenger traffic are largely--and mail traffic entirely--beyond their control the cost of handling mail and passengers has been steadily increasing, and, as revenue has not increased, the net revenue or margin of profit has been cut to a point where it is unremunerative. The argument advanced by advocates of reduced mail pay, that increasing density permitted economies and that lower rates would yield more net, is not applicable when the carriers' hands are tied and measures of economy so successfully applied to handling freight are prohibited. The following will illustrate this: On routes where pouch service is used mail is handled with express and baggage without much increase of cost over other passenger traffic. A somewhat greater mail traffic obliges the railroads to furnish apartment cars, at increased expense and dead weight for the postoffice feature, but still permitting the railroads to carry other traffic in the same car. A still further increase in weight means the establishment of full R. P. O. lines for which the railroads receive extra, but inadequate, compensation, these cars being used for no other class of traffic and adding largely to the weight and cost of train service. Even after the route has been made an R. P. O. route, the railroads are not permitted to economize by carrying more mail in the car, and as traffic density grows the roads must under the requirements of the Department add more cars, almost in proportion to the business, as the loads carried in R. P. O. cars, as shown by recent special weighing, average only 2¾ tons, and many of them return empty--for which empty haul the railroads often receive no pay. When the mail business has assumed very large proportions and the R. P. O. cars have multiplied in ratio therewith, special trains are then added to carry the bulk of the mail, being run at very high speed and adding to the railroad expense account in a far higher degree per unit of business than any other class of traffic.