No such bonds shall be issued in such a manner as to increase the indebtedness of the said city, but such bonds shall be delivered in payment and discharge of sums which it shall be required to pay by the judgment or decree of any court, at least equal to the principal sum of the bonds so delivered; or such bonds shall be sold as directed by the council of the city, or, in the absence of such directions, by the city treasurer, and the proceeds thereof shall be applied only to the payment of the sums aforesaid; but all such bonds so sold shall be delivered at the same time that the sums aforesaid shall be paid and discharged.