But the world is round,' said Peter. 'It is not,' said Sean. 'How can you say such a wicked thing? Fie.' 'But it is,' cried Peter, 'and if we go on, we shall come back to where we began.' 'Of course we shall,' replied Sean, 'but that is because it is shaped like a cheese. You may go round, as Loegaire did: but you may not go up or down for ever, or you will fall off the ends, as Maire nic Phiarais did and we ourselves almost when we went too far south of the Horn. The whole world knows that.