As to railroad, telegraph, and sleeping-car companies engaged in interstate commerce the rule thus is, as stated by the court in Adams Express Co. v. Ohio State Auditor,33 "that their property in the several States through which their lines of business extends may be valued as a unit for the purposes of taxation, taking into consideration the uses to which it is put -and all the elements making up aggregate value, and that a proportion of the whole fairly and properly ascertained may be taxed by the particular State, without violating any federal restriction.34 The valuation is, thus, not confined to the wires, poles, and instruments of the telegraph company; or the roadbed, ties, rails, and spikes of the railroad company; or the cars of the sleeping-car company, but includes the proportionate part of the value resulting from the combination of the means by which the business was carried on, a value existing to an appreciable extent throughout the entire domain of operation. And it has been decided that a proper mode of ascertaining the assessable value of so much of the whole property as is situated in a particular State is, in the case of railroads, to take that part of the value of the entire road which is measured by the proportion of its length therein to the length of the whole (Pittsburg, C, C. & St L. R. Co. v. Backus, 154 U. S. 439; 14 Sup. Ct. Rep. 1114; 38 L. ed. 1031) ; or taking as the basis of Constitutional Limitations UPon Taxing Powers. 951 assessment such proportion of the capital stock of a sleeping-car company as the number of miles of railroad over which its cars are run in a particular State bears to the whole number of miles transversed by them in that and other States (Pullman's Palace Car Co. v. Pennsylvania, 141 U. S. 18; 11 Sup. Ct. Rep. 870; 35 L. ed. 613) ; or such a proportion of the whole value of the capital stock of a telegraph company as the length of its lines within a State bears to the length of its lines everywhere, deducting a sum equal to the value of the real estate and machinery subject to local taxation within the State (Western U. Tel. Co. v. Taggart, 163 U. S. 1; 16 Sup. Ct. Rep. 1054; 41 L. ed. 49)." 35

33 166 U. S. 194; 17 Sup. Ct. Rep. 305; 41 L. ed. 683.

34 Citing Western U. Tel. Co. v. Mass., 125 U. S. 530; 8 Sup. Ct. Rep. 961; 31 L. ed. 790; Mass. v. Western U. Tel. Co., 141 U. S. 40; 11 Sup. Ct. Rep. 889; 35 L. ed. 628; Maine v. Grand Trunk R. Co., 142 U. S. 217; 12 Sup. Ct. Rep. 121; 35 L. ed. 994; Pittsburg, C. C. & St. L. R. Co. v. Backus, 154 U. S. 42l; 14 Sup. Ct. Rep. 1114; 38 L. ed. 1031; Cleveland, C. C. & St. P. R. Co. v. Backus, 154 U. S. 439; 14 Sup. Ct. Rep. 1122; 38 L. ed. 1041; Western U. Tel. Co. v. Taggart, 163 U. S. 1; 16 Sup. Ct. Rep. 1054; 41 L. ed. 49; Pullman Palace Car Co. v. Penn., 141 U. S. 18; 11 Sup. Ct. Rep. 876; 35 L. ed. 613.