If any person shall wilfully do, or cause to be done, any act, whereby any work, materials, or property whatsoever, erected or used, or hereafter to be erected or used, within the city of New York, or elsewhere, by the said Mayor, Aldermen and Commonalty, or by any person acting under their authority, for the purpose of procuring or keeping a supply of water, shall in any manner be injured, such person, on convictiqn thereof, shall be deemed guilty of a misdemeanor. 17. All contracts for materials, or for the construction of the work, shall be made in writing, and of each contract three copies shall be taken, which shall be numbered with the

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same number, and endorsed with the date of the contract, with the name of the contractor, and a summary of the work to be done, or materials furnished. 18. One of such copies shall be retained by the Commissioners, another shall be deposited with the Comptroller of the city. 19. Public notice shall be given of the time and place at which sealed proposals will be received for entering into contracts.

20. All sealed proposals for contracts shall be for a sum certain as to the price to be paid or received and no proposition, which is not thus definite and certain, or which ;

contains any alternative, condition, or limitation as to price, shall be received or acted upon.

21. No more than one proposition shall be received from anyone person for the same contract, and all the propositions of the person offering more than one, shall be rejected.