Every ordinance granting or extending any franchise shall contain all the terms and conditions of the franchise. A franchise shall be without any validity whatever until it has been accepted by the grantee, and until it has been given adequate publicity, either by the publication of the franchise verbatim in the official paper of the city at least once a week for four successive weeks after its passage, or by the posting of authentic copies -of the franchise upon bulletin boards in at least ten of the most public places in the city for a period of thirty days after its passage. Nothing herein contained shall be construed as in any way preventing the electors from exercising their powers under the referendum to reject such franchise.