If three-fifths of the votes cast at such election be in favor of issuing said bonds, the said board of county commissioners shall make an order that said bonds shall be issued, which said bonds shall be duly executed by the president and secretary of the board of irrigation commissioners of said district and attested with the seal thereof, and shall be countersigned by the chairman of the board of county commissioners and the county clerk and attested with the seal thereof; and said bonds shall be duly registered in the manner provided by law.