For this the Roman alphabet must have been used.  The Ogam script consists of a number of short lines straight or slanting, and drawn either below, above, or through one long stem-line.  This stem-line is generally the sharp angle between two faces or sides of a long upright rectangular stone.  Thus four cuts to the right of the long line stand for S; to the left of it they mean C; passing through it, half on one side and half on the other, they mean Z. The device was rude, but it was applied with considerable skill, and it was undoubtedly framed with much ingenuity.  The vowels occurring most often are also the easiest to cut, being scarcely more than notches on the edge of the stone.  The inscription generally contains the name of the dead warrior over whom the memorial was raised; it usually begins on the left corner of the stone facing the reader and is to be read upwards, and it is often continued down on the right hand angular line as well.

The language of the Ogam inscriptions is very ancient and nearly the same forms occur as in what we know of Old Gaulish.  The language, in fact, seems to have been an antique survival even when it was first engraved, in the third or fourth century.  The word-forms are probably far older than those used in the spoken language of the time.  This is a very important conclusion, and it must have a far-reaching bearing upon the history of the earliest epic literature.  Because if forms of language much more ancient than any that were then current were employed on pillar-stones in the third or fourth century, it follows that this obsolescent language must have survived either in a written or a regularly recited form.  This immediately raises the probability that the substance of Irish epic literature (which was written down on parchment in the sixth or seventh century) really dates from a period much more remote, and that all that is purely pagan in it was preserved for us in the same antique language as the Ogam inscriptions before it was translated into what we now call “Old Irish.”

The following is the Ogam alphabet as preserved on some 300 ancient pillars and stones, in the probably ninth-century treatise in the Book of Ballymote, and elsewhere: 

[Illustration:  Ogam Alphabet]

There are a great many allusions to this Ogam writing in the ancient epics, especially in those that are purely pagan in form and conception, and there can be no doubt that the knowledge of letters must have reached Ireland before the island became Christianized.  With the introduction of Christianity and of Roman letters, the old Ogam inscriptions, which were no doubt looked upon as flavoring of paganism, quickly fell into disuse and disappeared, but some inscriptions at least are as late as the year 600 or even 800.  In the thoroughly pagan poem, The Voyage of Bran, which such authorities as Zimmer and Kuno Meyer both consider to have been committed to parchment in the seventh century, we find it stated that Bran wrote