“ It is, of course, true that if the pipe line was constructed solely to carry oil for particular producers under strictly private contracts and never was devoted by its owner to public use, that is, to carrying for the public, the state could not, by mere legislative fiat or by any regulating order of a commission, convert it into a public utility or make its owner a common carrier ”

“ The statute declares that every private corporation or individual operating 'any pipe line or any part of any pipe line * * * for the transportation of crude oil, * * * directly or indirectly, to or for the public, for hire, * * * and which said pipe line * * * is constructed or maintained upon, along, over or under any public highway, and in favor of whom the right of eminent domain exists,' shall be deemed a common carrier and subject to the provisions of a prior act investing the Railroad Commission with extensive powers over the rates and practices of those who operate public utilities. ”

“ That some of the contracts before mentioned were entered into before the statute was adopted or the order made is not material. A common carrier cannot by making contracts for future transportation or by mortgaging its property or pledging its income prevent or postpone the exertion by the state of the power to regulate the carrier's rates and practices. Nor does the contract clause of the Constitution interpose any obstacle to the exertion of that power. ”