The right to enact ordinances for any metropolitan city is hereby granted to the qualified electors of such city, but such grant is made upon the following conditions and in addition to the right herein granted to the council to legislate: Whenever qualified electors of any such city equal in number to fifteen percent of the vote cast at the last preceding city election petition the council to enact a proposed ordinance, it shall be the duty of the council to either enact such ordinance without amendment within thirty days or submit the same to a vote of the people at the next election held within such city regardless of whether such election be a city, county or state election. Whenever such proposed ordinance is petitioned for by qualified electors equal in number to twenty-five percent of the votes cast at the last preceding city election and such petition requests that a special election be called to submit the proposed ordinance to a vote of the people in the event that the council shall fail to enact the same, it shall be the duty of the council to either enact such ordinance without amendment within thirty days or submit such ordinance to a vote of the people at a special election called by the council for that purpose. The date of such election shall not be less than fifty days nor more than seventy days after the filing of the petition for the proposed ordinance. The petition herein provided for shall be in the general form and as to signatures and verification as provided in section 14-212, shall be filed with the city clerk, and if there be no city clerk, then with such other officer having charge of the records of the city council. Said officer shall immediately ascertain the percent of the voters signing such petition and transmit his findings, together with such petition, to the council. In the event the council shall fail to enact such ordinance, the council shall submit the same to a vote of the people of such city as herein provided. The mayor shall issue a proclamation notifying the electors of such election at least fifteen days prior to such election, and the council shall cause to have published a notice of the election, and a copy of such proposed ordinance once in each of the daily newspapers of general circulation in the city, and, if there be no daily newspaper published within such city, then once in each weekly newspaper of general circulation in such city, such publication to be not more than twenty nor less than five days before the submission of the proposed ordinance to the electors. All proposed ordinances shall have a title which shall state in a general way the purpose and intent of such ordinance. The ballots used when voting upon such proposed ordinance shall contain the following: For the ordinance (set forth the title thereof) and Against the ordinance (set forth the title thereof). If a majority of the electors voting on the proposed ordinance shall vote in favor thereof such ordinance shall thereupon become a valid and binding ordinance of the city. An ordinance so adopted shall not be altered or modified by the council within one year after the adoption thereof by the people. Any number of proposed ordinances may be voted upon at the same election in accordance with the provisions of this section; PROVIDED, the same measure, either in form or essential substance, shall not be submitted more often than once in two years.