"The property of a railroad company for purposes of taxation consists of its realty, its local personalty, its rolling stock, its choses in action, and its franchises. The franchise is a privilege conferred by the charter of incorporation, namely the right to exercise all the powers granted in the mode prescribed for the purpose of profit. It is a unit not confined to any one county in which it may be exercised. * * * * * "Obviously, after ascertaining the value of the entire franchise in the State as a unit, no more approximate or just division of this value can be made for purposes of taxation than to allot it among the counties through which the track runs in proportion of the entire length of track in the county to the entire length of track in the State.... "The roadway itself of a railroad depends for its value upon the traffic of the company and not merely upon the narrow strip of land appropriated for the use of the road, and the bars and cross-ties thereon. The value of a roadway at any given time is not the original cost, nor, _a fortiori_, its ultimate cost after years of expenditure in repairs and improvements. On the other hand, its value cannot be determined by ascertaining the value of the land included in the roadway assessed at the market price of adjacent lands, and adding the value of the cross-ties, rails, and spikes. The value of land depends largely upon the use to which it is put and the character of the improvements upon it." The mileage basis of apportionment is sustained in the following and other cases: State Railroad Tax Cases 92 U. S., 608 Delaware Railroad Tax Case 18 Wall., 206 Erie Railway _vs._ Pennsylvania 21 Wall., 492 Western Union Telegraph Company _vs._ Mass 125 U. S., 530 Pullman Palace Car Company _vs._ Pennsylvania 141 U. S., 18 Maine _vs._ Grand Trunk Railway 142 U. S., 217 Pittsburg, Cincinnati, Chicago, and St. Louis Railway 154 U. S., 430 _vs._ Backus Therefore this basis of division of values between territorial units appears to be well established by precedent. This is in a measure unfortunate, as certain classes of property cannot be apportioned equitably in this way, unless the value of a railroad be determined, and then that value allocated between different territorial units in proportion to mileage, without any regard to the location of any structure or series of structures in any State or county, the track-mileage basis must be looked upon as a method of apportionment which is subject to modification or which will lead to error. In an Indiana tax case, Cleveland, Cincinnati, Chicago, and St. Louis Railway _vs._ Backus (154 U. S., 444), the late Justice Brewer, of the Supreme Court, in handing down the judgment, said: