The like difficulty meets us in both Welsh and Irish: that of deciding how far the mediæval scribes and scholars doctored the older material which fell into their hands. But in Welsh, the separation of the primitive from the mediæval element is often even a more difficult task than in Irish. In sketching the early course of Welsh literature, we cannot do better than turn to the striking instance afforded by the name and fame of Merlin. In legendary Welsh history, Merlin appears under almost as many guises as he does in the pages of Malory's 'Morte d'Arthur.' Merddin Emrys (Ambrosius), Merddin Sylvester (Merlin the Wild), Merddin ab Morvryn (or Merlin Caledonius),--his name and fame vary according to the chronicler. Of these, Merlin the son of Morvryn, the most tangible in the list, was also known as Caledonius, because the Kymry of the sixth century lived in that greater Wales which ranged as far north as the Caledonian Forest. After the terrible battle of Arderydd, Merlin, having seen his kindred all but obliterated, was seized, tradition tells us, with a frenzy, and thereafter his bardic utterances assumed a more and more mystical and oracular form. This, added to his mysterious and magnetic personality and wildly impressive personal presence, may well have led on in process of time, by gradual legendary accretions, to the final conception of a Merlin miraculous, supernatural, dæmonic! However this may be, nothing can be more instructive than to compare the late Merlin with the early Merlin, and to trace his phases in Welsh folk-tale, and define his poetry finally in the pages of the 'Black Book of Carmarthen.' The 'Black Book of Carmarthen,' in its strikingly decorative black and red manuscript, makes a wonderful testament of old Welsh poetry. If we could solve all its problems and read all that is written between its lines, we should be very near the great secret of the Druidic religion and of Celtic mythology, as well as the secret of Merlin's actual and imaginary effect in Welsh literature. The battle of Arderydd has been cited above as a determining event in Merlin's history. The opening poem in the 'Black Book of Carmarthen' is a remarkable rhymed dialogue between Merlin and Taliesin, some of whose lines are extremely imaginative and touching in their archaic simplicity. Merlin begins:-- "How sad is Merlin now! how sad! Keduyf and Kadvan--are they dead? The furious slaughter filled the field, And pierced was the Tryrwyd shield!" Taliesin replies:-- "His house-folk did not falter in the fight!" So it goes on, telling of the battle and its consequences, until one reaches at the end that mysterious verse which haunts the imagination and the ear of the reader. Merlin again speaks:-- "Sevenscore chieftains Were turned into spirits; In the wood of Celyddon Were they transformed.