Folktale, memoir, fiction, literary hoax, The Yellow Briar is all of these. Ostensibly the charming remembrance of an Irish orphan who escapes the Great Famine of 1840s Ireland and comes to the New World to seek a fresh start on the streets of Toronto and in the pioneer hinterland of Canada West (Ontario), the book was actually a fictional humbug perpetrated by John Mitchell, a Toronto lawyer, who first published the tale in 1933.Patrick Slater, the protagonist of the ''memoir,'' is said to have died in 1924 but not before setting his saga down on paper. And what an account it is! The Globe and Mail felt that the book ''gives a picture of Ontario to be found in no other work of fiction we know and has won for itself a permanent place in Canadian literature.'' If nothing else, Slater/Mitchell captures perfectly the lilt of the Irish and the wry wisdom of an old soul to paint an affecting portrait of trials and tribulations in a long-ago time.