Show MAKING TG MAPS 1 r Ye t 0 fr Four colors at most arc are needed to dl distinguish dis- dis h the surfaces of or separate dl dis 1111 on an any pl piano lj map so 0 that no two with n a common boundary are ore tinted alike On this diagram A B and C ere adjoin III lug liiK districts on a plane surface and und X bord borders rs In one wa way or another upon each It Is clearly impossible to Introduce a fifth area which shall so 80 adjoin these four districts as to need another r tint Unto 1 I IQ 4 |