The original circular of the Post Office Department contained certain "notes," to the effect that in reporting the length of postal cars and apartment cars, and the space therein used for mails, the railroad companies should only report the length or space "authorized" by the officials of the Department; also that in reporting space used in cars for what is known as the "Closed Pouch Service," the railroads should make an arbitrary allowance of six linear inches across the car for the first 200 pounds or less of average daily weight of pouch mail and three linear inches for each additional 100 pounds. These directions were modified by the subsequent circular letter of the Department, dated October 23, 1909. This letter, among other things, directs the company to take credit for "surplus" space in post office cars and apartment cars, if actually used for the storage of mails. The practical difficulties attending the measurement and proper allotment of the space used for the mails in postal and other cars run on a passenger train will be better understood when it is known that such space is or may be described in at least eight different ways, and is actually used on the Burlington road as follows, namely: 1. Space in post office cars specially "authorized" (43.03%). 2. Space in apartment cars specifically "ordered" (20.69%). 3. Space ordered in post office cars operated in lieu of apartment cars (4.3%). 4. Additional space actually used for storage of mails when the railroad company operates larger post office or apartment cars than the authorization calls for (1.5%). 5. Space in storage cars actually used for mails (12.87%). 6. Space in baggage cars used for closed pouch mails (4.06%). 7. The return deadhead movement of space ordered and required in one direction only (8.35%). (Ninety-five per cent of all the "space" shown in these returns for the Burlington, as used for the mails, comes within the foregoing seven classes, as properly authorized space about which no question can arise.) 8. "Surplus" space; that is, space furnished to the Government in post office and apartment cars in excess of actual requirements (5.2%). This five per cent is the only portion of the space claimed as used for mails regarding which any question can be raised, affecting the integrity of these returns. What is the correct view as to this five per cent? It is manifestly against the interest of the railroad company to furnish space for mails that is not required, and it will never furnish such space if it can be avoided. But the "requirements" of the Post Office Department are not fixed and certain quantities, by any means. It is entirely impracticable for any railroad company to keep on hand at all times a supply of cars of all lengths in order to meet exactly the requirements of the Department officials.