Section 5. When a ward has been divided into new voting precincts, or the voting precincts thereof have been changed, the aldermen shall forthwith cause a map or description of the division to be published, in which the new precincts shall be designated by numbers or letters and shall be defined clearly and, so far as possible, by known boundaries; and they shall cause copies thereof to be furnished to the registrars of voters, to the assessors, and to the election officers of each precinct so established. The aldermen shall cause copies thereof to be posted in such public places in each precinct of a ward so divided as they may determine or shall give notice by mail to each registered voter affected by such change of voting precinct.