When a petition, signed by qualified electors of a county equal in number to at least thirty-three and one-third per cent of all the votes cast within the county for governor in the last preceding general election, is filed with the board of supervisors praying for a change of the county seat, the board shall submit the question of such change to the qualified electors of the county at a special election to be held for that purpose, or at the next general election of county officers. The petition for the change shall be substantially in the form, and signed and verified as generally provided for initiative petitions.