A practical way of colouring any map is this. Number the districts in
succession, always numbering a district which has less than six bounda
ries, not including those boundaries which have a district already num
bered on the other side of them. When the whole map is numbered, begin
ning sith the highest number, letter the districts in succession with
four letters, a, b, c, d, rearranging the letters whenever a district
has four round it. so that it may have only three, leaving one to lett
er the district with. When thr whole map is lettered, colour the distr
icts, using different colors for districts lettered differently.