Kempe revisited

A practical way of colouring any map is this. Number the districts in succession, always numbering a district which has less than six boundaries, not including those boundaries which have a district already numbered on the other side of them. When the whole map is numbered, beginning 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 letter the district with. When thr whole map is lettered, colour the districts, using different colors for districts lettered differently.