Should any of the lands assessed under this chapter be taken for or dedicated to public use, for highway or any other public purpose, before the taking or dedication shall be complete or take effect there shall be paid to the county treasurer a sum equal to the principal of the unpaid assessment upon said land at its proportionate rate per square foot, with interest thereon for one year at a rate determined by the board; and the treasurer shall credit the principal sum paid to the unpaid installments upon the tract as originally assessed.