With reference to the foregoing it is perhaps worthy of special mention that the right of public service corporations to fix their own charges or tolls is one which the legislature may grant, and, when granted, constitute a contract which the legislature may not subsequently impair.47 It does not need to be said, however, that this agreement upon the part of the State not to exercise its regulative power is one that must be explicitly stated. A general grant to the corporation of the power to fix, or alter its charges or tolls as it may think proper, is not an abdication by the State of its power of control.48 Nor does a grant to the corporation of a power to fix its own rates, provided they are not unreasonable, have this effect;49 nor does a grant of power to fix the charges, provided they be not in excess of a specified rate, prevent the State from later fixing a lower rate.50 And, generally, the reservation by the State of a power to amend or revoke the charter, carries with it a power to regulate the charges that may be made.51

The creditor should be no otherwise acted upon than as even* other possessor of moneys, and, consequently, the money he receives from the public can then only be a fit subject of taxation when it is entirely separated' (from the contract), 'and thrown undistinguished into the common mass.' 3 Hamilton, Works, 514 et seq. Thus only can contracts with the State be allowed to have the same meaning as all other similar contracts have."

43 100 U. S. 548; 25 L. ed. 710.

44 140 U. S. 387; 13 Sup. Ct. Rep. 110; 36 L. ed. 1018.

45 94 U. S. 113; 24 L. ed. 77.

46 C. B. & Q. R. Co. v. Iowa, 94 U. S. 155; 24 L. ed. 94; Peik v. C. & N. Ry. Co., 94 U. S. 164: 24 L. ed. 97; C. M. & St. P. R. R Co. v. Ackley, 94 U. S. 174: 24 L. ed. 99.