The right of the States to tax property, as such, of companies doing an interstate commerce business, is determined by the same principles as those stated in Union Pacific R. R. Co. v. Peniston4 with reference to the taxation by the States of federal agencies, namely, that "state taxation is dependent, not upon the nature of the agents, or upon the mode of their constitution, or upon the fact that they are agents, but upon the effect of the tax; that is, upon the question whether the tax does in truth deprive them of power to serve the government as they were intended to serve it, or does hinder the efficient exercise of this power. A tax upon their property has no such necessary effect. It leaves them, free to "discharge the duties they have undertaken to perform. A tax upon their operation is a direct obstruction to the exercise of federal powers."

95 Subject, of course, to necessary quarantine provisions.

96 Cf. Prentice and Egan, Commerce Clause, p. 212ff.

97 11 Pet. 102; 9 L. ed. 648.

98 5 How. 504; 12 L. ed. 256.

99 7 How. 283; 12 L. ed. 702. 1 6 Wall. 35; 18 L. ed. 745.

2 92 U. S. 259; 23 L. ed. 543.

3 107 U. S. 59; 2 Sup. Ct. Rep. 87; 27 L. ed. 383. 4 18 Wall. 5; 21 L. ed. 787.

In Postal Telegraph Cable Co. v. Adams5 the court say: "It is settled that where by way of duties laid on the transportation of the subjects of interstate commerce, or on the receipts derived therefrom, or on the occupation or business of carrying it on, a tax is levied by a State on interstate commerce, such taxation amounts to a regulation of such commerce and cannot be sustained. But property in a State belonging to a corporation, whether foreign or domestic, engaged in foreign or interstate commerce, may be taxed, or a tax may be imposed on the corporation on account of its property within a State, and may take the form of a tax for the privilege of exercising its franchises within the State, if the ascertainment of the amount is made dependent in fact on the value of its property situated within the State (the exaction, therefore, not being susceptible of exceeding the sum which might be leviable directly thereon), and if payment be not made a condition precedent to the right to carry on the business, but its enforcement left to the ordinary means devised for the collection of taxes. The corporation is thus made to bear its proper proportion of the burdens of the government under whose protection it conducts its operations, while interstate commerce is not in itself subjected to restraint or impediment. . . . Doubtless, no State could add to the taxation of property according to the rule of ordinary property taxation, the burden of a license or other tax on the privilege of using, constructing or operating an instrumentality of interstate or international commerce, but the value of property results from the use to which it is put and varies with the profitableness of that use, and by whatever name the exaction may be called, if it amounts to no more than the ordinary tax upon property or a just equivalent therefor, ascertained by a reference thereto, it is not open to attack as inconsistent with the Constitution. (Cleveland, C. C. & St. L. E. Co. v. Backus, 154 El S. 439; 14 Sup. Ct. Rep. 1122; 38 L. ed. 1041)."

6 155 U. S. 688; 15 Sup. Ct. Rep. 268; 39 L. ed. 311.