The governing body of any city of the first class which owns and operates a hospital is hereby authorized to issue general obligation bonds of such city in an amount not exceeding one million dollars ($1,000,000) for the purpose of paying the cost of constructing an addition to the hospital owned by such city and furnishing and equipping the same, and otherwise improving said hospital and the facilities thereof: Provided, That no such bonds shall be issued until the question of their issuance shall have been submitted to a vote of the electors of such city at a regular city election or a special election called for such purpose and a majority of the legal electors voting on the question shall have voted in favor of their issuance: Provided further, That if the governing body of any such city shall have submitted such a question to a vote of the electors of such city prior to the effective date of this act, with or without authority of law, and a majority of the legal electors voting on the question shall have voted in favor of the issuance of the bonds, said city may issue bonds for such purposes in an amount not exceeding the amount voted at such election without submitting the question at another election and said election and all proceedings in connection therewith are hereby validated and confirmed. Said bond election shall be called, held, conducted and canvassed and all bonds issued under the authority of this act shall be issued, registered, sold, delivered and retired as provided by the general bond law.