The devil with which we are acquainted is a character unknown to Greek or Roman mythology; this devil was a later invention; but his identity with the genii, or jinns of the 'Arabian Nights,' the Dïvs of Persian history, is clear enough. Ahriman, the evil spirit, king of the realms of darkness and of fire, was apparently the progenitor of Satan, as Vritra was of Ahriman. Both these ancient arch-fiends appeared as serpents in form, and were myths representing the darkness, slain by the light, or the sun-god, in the one case called Indra, in the other Ormuzd. The medieval devil with horns and hoofs does not appear in the records of Judaism. He is an outgrowth of the moral principle of the Christian era; and traced to his origins he is simply a personification of the adversary in the never-ending struggle on earth between light and darkness. That struggle is not, in nature, a moral one; but it remains to-day, as it was in the beginning, the best type we have of the battle between right and wrong, and between truth and error. When God said, 'Let there be light,' the utterance became the symbol and guide of virtue, of brave endeavour, and of scientific research, until the end.