"The specific items which constitute this total cost are not definitely known to the Department. However, as to the cost of lighting, cleaning, repairs, etc., the General Superintendent of Railway Mail Service furnished the following estimates before the Commission to investigate the postal service in 1899, viz.: Lighting, $276; heating, $365; cleaning, water, ice, oil, etc., $365; repairs, $350; proportion of original cost of car (estimating the life of a car at fifteen years and the original cost at $6,000), $400; total, $1,756. Recent inquiry gives the following as the approximate cost of maintaining a car at the present time: Lighting (electric), $444; heating, $150; cleaning, $360; repairs, $300; oil and brasses, $120; interest on cost of car (at $7,500), $300; annual deterioration (estimating the life of a car at twenty years), $375; total, $2,049. These figures give the cost of a car built according to the Department's standard specifications. The cost of modern steel cars being built by some of the railroad companies is from $14,000 to $15,000. "The compensation received by a railroad company for operating a car and carrying the mails in it would be approximately as follows: "The pay for a 60-foot car at $40 a track mile per annum, for a track mileage of 150 miles, would be $6,000. The average load of a 60-foot car, according to statistics obtained recently, is 2.83 tons. The rate per ton of an average daily weight of 50,000 pounds carried over the route is $25.06. At this rate the company would receive $10,637.97 per annum for the average load of mail hauled in the car. This sum added to the specific rate for the railway post office car ($6,000), makes the total pay for the car and its average load $16,637.97 per annum. "Senator Vilas' argument was based upon the theory that the rates fixed for railroad transportation alone, based on the weights of the mails carried, are adequate compensation for all services rendered, including the operation of railway post office cars, and that, therefore, the railroad companies would be required to operate postal cars owned by the Post Office Department for the compensation allowed by law for the weight of mails alone, including apartment-car space and facilities. Such theory is not justified by the facts, as will appear from the following: