These three Orders of Druids, Bards, and Brehons were, as we have seen, close corporations, invested with many privileges, and communicating a professional knowledge for the most part by oral instruction to their disciples. This course of instruction was very long and elaborate, sometimes extending to a period of twenty years. It included, as in more modern times, various steps or degrees of learning, the highest of which always was that of Ollamh or Doctor, whether in law, poetry, or divinity. The ordinary course was twelve years, and each year's work seems to have been as carefully fixed as in a modern college or university. A great portion of the work, after the purely elementary studies, consisted in getting off by rote either the bardic tales, or legal maxims with their leading cases, or historical poems and genealogies. This included a very perfect knowledge of topography, chronology, and family history. Versification of a very artificial and complicated character was also a portion of the programme. Besides the students had undoubtedly, at least in pre-Christian times, some kind of 'secret' language known only to the initiated. It would seem as if each profession or school had its own peculiar Oghamic alphabet, the key of which was known only to themselves; but in this matter we have no certain knowledge, and are left almost entirely to pure conjecture. Hereafter we shall see that the legal relations between the professor and his pupils were definitely ascertained, and are laid down in that portion of the Brehon Code which deals with the Law of Social Connections. IV.--THE OGHAM ALPHABET. We shall see presently, when treating of the literary history of Cormac Mac Art, that the use of letters, and most probably of Roman letters, was quite common in Erin before the coming of St. Patrick. Besides the Roman alphabet there was, however, an earlier and ruder alphabet, which seems to have been used in Erin even in the pre-historic times. This is called the Ogham alphabet which has had a very strange and curious history. It is a singular fact that all knowledge of the Ogham alphabet, as well as of the existence of any inscriptions written in its peculiar characters, had for a considerable period completely disappeared from the minds of Irish scholars. Yet the Ogham score was all the time contained in the _Book of Ballymote_,[23] and the key to its interpretation also. Inscribed stones too were thrown about unnoticed in various parts of the country down to the year 1820, when Mr. John Windele discovered the first inscription in the co. Cork.