We may compare the Chthonian ceremony of swearing, in which the slain animal was conceived as at once symbolising and magically inducing a similar fate in case of perjury. The Roman formula is well known. Livy tells[113] how a certain M. Valerius, one of the Fetiales, or Roman priests, swore on behalf of the Roman State, to the Almighty Juppiter, in a treaty with ancient Alba. ‘Audi, Iuppiter: audi, pater patrate populi Albani: audi tu, populus Albanus ... si prior defexit publico consilio, dolo malo, tu illo die, Iuppiter, populum Romanum sic ferito ut ego hunc porcum hic hodie feriam: tantoque magis ferito quanto magis potes pollesque.’ Now, all such ceremonies, simple as they may appear, were hedged round with the most minute regulations as to formulae and procedure, and were thus removed from the competence of ordinary individuals. Moreover, each locality developed differences of usage which, however slight, could never be ignored. Herodotus,[114] speaking of homicide purgation, implies that all Greeks used the same rites. But that there were minor local variations may be inferred, perhaps, from a peculiar ceremony in the _Oedipus Coloneus_ of Sophocles. Oedipus, having gone as an exile from Thebes to Attica because he had slain his father, is told[115] that he cannot hold converse with the Athenians while he is still uncleansed. The ban is removed when he is admitted to ‘purgation,’ but for the due performance of the rite he is entirely dependent on local direction. We shall give the relevant dialogue between Oedipus and the Chorus[116]: _Oed._ Kind sir, Be my good guide. I will do all thou biddest. _Ch._ Propitiate these holy powers, whose grove Received thee when first treading this their ground. _Oed._ What are the appointed forms? Advise me, sirs. _Ch._ First see to it that from some perennial fount Clean hands provide a pure drink-offering. _Oed._ And when I have gotten this unpolluted draught? _Ch._ You will find bowls, formed by a skilful hand, Whose brims and handles you must duly wreathe. _Oed._ With leaves or flocks of wool, or in what way? _Ch._ With tender wool ta’en from a young ewe-lamb. _Oed._ Well, and what follows to complete the rite? _Ch._ Next, make libation toward the earliest dawn.... _Oed._ With what contents Must this[117] be filled? Instruct me. _Ch._ Not with wine, But water and the treasure of the bee. _Oed._ And when leaf-shadowed Earth has drunk of this, What follows? _Ch._ Thou shalt lay upon her then From both thy hands a row of olive twigs Counting thrice nine in all—and add this prayer— _Oed._ That is the chief thing—that I long to hear.