The Celtic heroic saga in the British islands may be divided into the two principal groups of Gaelic (Irish) and Brython (Welsh), the first, excluding the purely mythological, into the Ultonian (connected with Ulster) and the Ossianic. The Ultonianis grouped round the names of King Conchobar and the heroCuchulainn, " the Irish Achilles," the defender of Ulster against all Ireland, regarded by some as a solar hero.
The second cycle contains the epics of Finn (Fionn, Fingal) mac Cumhail, and his son Oisin (Ossian), the bard and warrior, chiefly known from the supposed Ossianic poems of Macpherson.
The list of his works includes hymns and national songs - among others, the famous Chant du depart; odes, Sur la mort de Mirabeau, Sur l'oligarchie de Robespierre, &c.; tragedies which never reached the stage, Brutus et Cassius, Philippe deux, Tibere; translations from Sophocles and Lessing, from Gray and Horace, from Tacitus and Aristotle; with elegies, dithyrambics and Ossianic rhapsodies.
At the age of ten he composed a tragedy under the inspiration of Caesarotti's translation of the Ossianic poems. On the marriage of his twin sister Rosina with a maternal cousin at Lyons he went to reside in that city, devoting himself during four years to the study of French literature.
Numerous parallels exist between the Arthurian and early Irish heroic cycles, notably the Fenian or Ossianic. This Fenian cycle is very closely connected with the Tuatha de Danaan, the Celtic deities of vegetation and increase; recent research has shown that two notable features of the Arthurian story, the Round Table and the Grail, can be most reasonably accounted for as survivals of this Nature worship, and were probably parts of the legend from the first.