The governing body of any city of the second class located in a county having a population of not less than twenty thousand nor more than twenty-five thousand and having an assessed tangible valuation of not less than thirty-seven million five hundred thousand dollars nor more than forty-five million dollars, is hereby authorized and empowered to issue the bonds of said city in an amount not exceeding fifty thousand dollars for the purpose of acquiring a site, building and equipping a hospital: Provided, That the question of issuing such bonds shall be submitted to the vote of the people at any regular city election or at an election called for that purpose, and no bonds shall be issued until a majority of the qualified electors who shall vote on the question at such election shall have declared by their votes in favor of issuing said bonds. Said election may be called by the governing body upon its own motion and shall be called by the governing body upon petition of at least forty percent of the qualified electors of such city.