An interesting, hard-to-classify curio that might have been a one of its kind classic with more intelligent editing.""Travellers"" are Scottish tinkers, tent-based wanderers who have been the featured rogues and vagabonds of Celtic folklore for centuries and who still rove the Western Highlands in summer, mending pots and selling handmade baskets. Williamson, who narrates these 12 traditional tales, is him-self a ""traveller,"" born in 1928 to a family of 16 children. A gifted storyteller, he has been responsible for bringing the rich oral tradition of this now-dwindling group to a wider audience. The tales range from the animal fables favored by the smallest travellers to the ""burker"" (body-snatcher) stories preferred by the teen-agers. At their best, the travellers' stories are both tough-minded and moving: a group of farm animals, banding together to escape the slaughterhouse, outwits a band of thieves; a boy cursed to be a ""hedgehurst"" (hedgehog) sets up a beautiful but lonely kingdom in mid-forest, eventually tricking a visiting king into giving him a bride. Several weaker tales, however, are predictable and sentimental: ""The Night of Peace"" is a disappointing Christmas fable, and ""Mary and the Seal"" is an oddly bloodless ""silkie"" story. (Silkies are the enchanted seals of the Hebrides who seduce unwary virgins.) The only serious problem here is nonetheless a constant irritation: a garrulous and largely self-evident editorial commentary that runs to glosses of perfectly easy Scotticisms (""bonnie""; ""ken"") and lengthy digressions on the Scottish double negative. Though it consists of stories directed to children, this will probably be of most interest to folklore buffs. The stories, transcribed from tapes, have a rough edge and a slow, repetitive pacing that's not likely to appeal to children habituated to such flashier stuff as Papa Smurf and He-Man. More's the pity.