These gentlemen were not engaged in any detailed work on the appraisal; they came to the work for one week each month with minds entirely clear of all confusion raised by issues of detail, and were thus enabled to pass as a court upon all matters laid before them. Their association was of inestimable value in giving confidence to the members of the staff. The many years of railway service of Messrs. Chanute and Vaughn, and their unquestioned ability in that special field of engineering, gave the stamp of finality to points decided by them. The special knowledge of Mr. Hansel in the field of signal engineering, and his known ability as an expert in organization and administration, were of the greatest value. The service of Professor Greene was that of the analyst and logician; his clear and judicial mind enabled him to formulate the final arguments in many cases under consideration. The writer wishes to make it perfectly clear that he has not attempted to minimize the work of Professor Cooley by stating the exact relation of the many engineers on the staff to this work, but to bring out and emphasize the fact that no one man, or no two or three men, were responsible for any single part, but that the whole represents the best efforts of sixty or seventy experienced men working to secure a fair, honest, unprejudiced, engineering estimate along such lines as would eliminate, as far as possible, all errors of individual judgment. It has never been claimed for the work that it was perfect, or that it was entirely free from errors. It has been and is claimed for it that it probably represents as close and conservative an estimate of cost of reproduction and depreciation as it would be possible for any set of men to make under the conditions then existing. Professor Cooley was in constant touch with the work, knew its every detail, passed upon and approved every rule and order, presided at every conference, and nothing more than his activity, optimism, and constant watchful care and tireless energy kept the force at work day and night and brought about the prompt completion of the details. His recognized high standing, his remarkable ability as an executive and organizer, and his powers of diplomacy, more than anything else, brought about the final acquiescence of the railroad managers and kept up the confidence of the State authorities; his personality pervades the entire work. After giving all due credit to the staff, and they were entitled to much credit, the real honor must go to Professor Cooley. It was his conception, his plan, and the brunt of the battle was his. Office and Field Methods. The preliminaries of the organization having been completed, and the forms prepared, a portion of the working force was brought on the ground, and the work was actively commenced. It was subdivided into four parts: (_1_) Office inspection, or inventory; (_2_) Field inspection; (_3_) Computation;