County bonds shall be authorized and issued as provided in N.H. Rev. Stat. Chapter 25 and 28, provided that a public hearing is held which shall be advertised at least 7 days before said public hearing, in some daily newspaper having a wide circulation in the county, giving the time and place of the hearing; and provided that not more than 14 days after said public hearing the county convention shall approve such bond issue by at least
2/3 of the county convention present and voting and provided further that a majority of the whole convention shall be present.