Section 26. The citizens of the said county of Fulton shall before the first day of September, on thousand eight hundred and fifty, raise by voluntary subscription at least eight thousand dollars toward the purchase of lots, the erection of public buildings, and the payment of the tax required by the State upon this act, and shall give security for the faithful payment thereof to the said county, in a judgment bond to be signed by three or more of their number, and approved by the commissioners appointed by the sixteenth section of this act, who shall cause said judgment bond to be filed of record. And said commissioners are further authorized and required to contract for the purchase of a lot or lots on which to erect the public buildings, which shall afterwards be conveyed to the county commissioners who may be elected in October, one thousand eight hundred and fifty, and to their successors in office for the use of the said county of Fulton.