Whenever a petition shall be presented to the board of county commissioners of any such county, signed by at least one thousand of the qualified electors thereof, requesting the submission of a proposition to levy an annual tax for the purposes mentioned in this act, it shall be the duty of the county commissioners of such county to cause such vote to be taken at the next general election to be held in such county: Provided, The same shall be held within sixty days after the time when such petition shall have been presented. Otherwise, said commissioners shall immediately call a special election for such purpose. Said special election shall be held within sixty days after the date upon which such petition shall have been presented.