Independently of being joined to any railroad in general, these economical railroads shall pass to the jurisdiction of the Minister of Transportation and Public Works and shall be obliged to enlarge their gauge to 1 meter, without other favors from the Government, there not being a supplementary term of the contract, if it is wanting for its termination in less than 60 years, when the gross receipts have reached 15,000 mibreis per kilometer during 3 successive years. Before this the railroad may pass to the Minister of Transportation and the gauge be widened, on his own account, when he shall think it to his interest, or by a new contract, when the Government thinks it necessary to have it done for the necessities of the administration or the defense of the country. Art. 55. In addition to the subvention per kilometer, there shall be given to these railroads all the indirect favors received by the other railroads of the country. Art. 56. The maximum term for a concession shall be 90 years, at the end of which the railroad will revert to the control of the Union. Art. 57. Under the right of experiment, the Government shall promote at once the following lines of economical railroads: 1. Parting from “Antiga Souzel,” or other point more convenient on the left bank of the Xingú and ascending the left side of the valley to the margin of the River Cariahy, with a branch which parting at a convenient point, shall go to the Tapajóz and ascend the right hand side of the valley until it reaches the S. Manoel which may appear advantageous, ascending the secondary valley and continuing to the dividing of the waters of the two principal rivers. 2. Parting from the confluence of the River Negro with the Branco and by the valley of the River Seruiny, gaining the right side of the valley by the Caratimani river and continuing to the upper Uraricoera, with a branch parting at a convenient point at the request of the upper Paduiry and a branch in the direction of the Villa Boa Vista. CHAPTER II Improvements for the navigation of the Rivers Branco, Negro, Purús and Acre Art. 58. The improvements necessary for effective navigation at any season of the year, for steamers drawing 3 feet, on the River Negro, between Santa Izabel and Cucuhy, on the River Branco, from its mouth to São Joaquin, on the River Purús, between Hyutanhã and Senna Madureira, and on the River Acre, from its mouth to Riosinho de Pedros, shall be contracted for by public bidding, or independently of bidding, with corporations sufficiently able, under the rule established by decree, number 6,368, Feb. 14, 1907 or others which may not be more onerous and may permit the assurance of the opening of navigation more rapidly on the sections of the rivers to be improved.