An assessment of damages so made shall be final and conclusive on the parties, their heirs and assigns, and give the petitioner, his heirs and assigns, forever, the right to keep up such dam as established; but the damages assessed, together with the costs, shall be paid to the respondent, or deposited for his use with the State Treasurer, before the water is flowed upon such lands and within sixty days after the proceedings on such petition have been ended. If such damages and costs are not so paid or deposited, the whole proceedings shall be of no effect.