Every man in the computing room was furnished a large bound blank-book, in which he was required to make all his notes and computations, no figures of any sort being made on loose paper. The name of each man was placed on his notebook, and each set of field and office inspection notes worked upon by him was signed with his initials. It was easy to trace the work of every man, and in the subsequent trial of the Tax Cases, every man in the service returned, and, not only testified as to his office and field inspection, but was able to turn to and identify all the computations made by him, and produce his original figures and memoranda. Very soon it became evident that such a volume of reports, notebooks, memoranda, maps, plans, pamphlets, and other data was being accumulated that, unless a special system was developed for filing and handling in the office, the confusion would be serious and costly. _Filing in Office._—The system of filing and record keeping had the merit of being simple and inexpensive. There was borne in mind, in devising this plan, the necessity of keeping all papers connected with one division of any road together, the need for reducing to a minimum the labor of filing and indexing, the constant use of papers, and their frequent withdrawal from the files, making it necessary that they could be at once located when they were not in the files. The vault in the appraisers' office was arranged so that large manilla envelopes, each of sufficient size to hold all the reports, notes, maps, etc., of each road or division, could be filed vertically. Each road was given a number; if there were several divisions, each division was given a letter, as "15-_A_," "15-_B_," etc., and each division was filed separately. Every report, book, map, or other paper was stamped with its road or division number and letter, and given a sheet number. In this manner every paper was identified, and could be at once placed. A record was kept in a book, describing every paper filed in each envelope. In issuing papers for work, the entire file was taken and kept together at all times. One man had charge of the filing and recording, and no one else was permitted to enter the vault. When a file was withdrawn, a receipt was taken, and was put in the place of this file; and when the papers were restored to the vault the receipt was destroyed. The system proved adequate, and was much less cumbersome than a more elaborate system of card indexing of separate papers could possibly have been. The net result of office and field inspection had been an inventory based on the railroad records, checked by a man in the field, with a percentage representing the field inspector's judgment as to depreciation, together with a considerable number of special data as to original cost, etc. It was now necessary to place figures of estimated cost of reproduction and depreciation in terms of money.