(_b_) _Unit Values._—The general reliability of the appraisal rests very largely on the reasonableness and fairness of the various prices which are applied to the different parts of the property in making the estimate of cost of reproduction. These unit prices should be determined before any actual figures are made. They should be made up from the most complete data available, and, before being tabulated, should be carefully reviewed by all the experienced men engaged on the appraisal, in order that no figure which is either too high or too low may be used. As a basis, the average of either 5 or 10 years should be used in preference to current prices on all such material and equipment as is fairly stable. Rail, and all forms of rail structures, machinery, locomotives, cars, etc., can be reduced to such a unit that averages can be secured which will eliminate the error due to a period of extreme high or low prices. In the case of such materials as lumber and ties, the price of which has been steadily rising, due to the growing scarcity of the material, a price based upon a long average is unfair to the corporation, and it would appear to be proper to use current prices. There can be no hard-and-fast rule which will be applicable to all appraisals. The unit prices must be such reasonable figures as can be sustained in Court. Their adoption should not be final until every possible test of their accuracy and reasonableness has been made. When they have been adopted, and such modification made as may be fair for certain territory, on account of local conditions, transportation facilities, or other consideration which may affect them, the adopted figures should be applied to all property alike. The use of different unit figures for different roads in the same territory is highly undesirable, and should be avoided. (_c_) _Right of Way and Real Estate._—The valuation work which has been accomplished during the past decade, and the study of values for taxation and rate-making, have brought into prominence the perplexing features of land values as applied to corporation property. It is comparatively simple to fix within very close limits the reproduction cost of tracks, bridges, locomotives, or any of the other elements of physical structure. Not so with the land. A few years' development may change farm land right of way into city right of way, surrounded by factories, or it may change desirable residential property adjacent to a road into slums.