We may say with some confidence that the nature of the lien of the second mortgage subsidy bonds of the United States depended, under the Thurman Act, upon the power of Congress to alter, amend, and repeal the terms of the Acts of 1862 and 1864 in respect to the security provided for the government loan. Court Decisions Now on the question of the meaning of the “saving clause” in the Act of 1864, the courts had not in 1897, and still have not, satisfactorily passed. That the clause did not authorize unlimited changes in the provisions of existing legislation was evident. The majority of the Supreme Court expressed the view in the sinking fund cases that the reserved power could not be used to undo what had already been done or to unmake contracts which had already been made, but that Congress could provide for what should be done in the future, and might even direct what preparation should be made for the due performance of contracts already entered into.[573] Under this interpretation the Supreme Court upheld the clauses in the Thurman law which required the Pacific railroads to pay certain moneys into a sinking fund. The same court in 1895 decided that a federal act which required bond-aided railroads to operate their own telegraph lines was a legitimate amendment of the clause of the Act of 1862 which authorized these companies to enter into agreements with specified private corporations for the rendering of telegraph service.[574] Again, in Menotti v. Dillon (1897), the court approved an amendment to the land-grant provisions of the Act of 1862 designed to quiet litigation in land cases in California;[575] and in Union Pacific v. Mason City and Fort Dodge, it sustained a law of 1871 which authorized the Union Pacific to issue bonds for the construction of a bridge across the Missouri River at Omaha, but required the company to permit the trains of all railroads terminating at the Missouri River at Omaha to use the new bridge up to a fair limit of its capacity and on payment of a reasonable compensation.[576]