It should not be understood that the writer maintains that taxation boards should not go beyond the valuation of physical property to arrive at a final basis for assessment. There are certain intangible elements which should be taken into consideration when taxing property, chief of which is the net income. It is only as far as physical valuations apply in either case that he considers that there should be uniformity. He does not approve at all of incorporating in an estimate of the physical value of a railroad property such an element as "adaptation and solidification of roadbed," which is credited with so much importance in the Minnesota valuation. In the first place, such an element is incapable of being measured in tangible terms and reduced to a dollars-and-cents basis; second, it cannot be reproduced in the sense that other property is reproduced, and its value does not appear in the capital account of the railroad; and third, it results from the action of the seasons on the one hand, and the working over of the roadbed by the maintenance forces on the other, the cost of which appears in operating expenses. One is constrained to believe that the engineer who insists on incorporating such an element in an appraisal of the physical value of a railroad is hard put to find material with which to swell his estimate. When noting the large difference in value per mile of the railroads of Minnesota, as compared with those of Michigan and Wisconsin—adjoining States—it would appear that undue prominence had been given to this and similar factors.