One of the most controversial myths in Scotland's cultural history is to be the subject of the National Gallery of Scotland's first touring exhibition.

The character of Ossian, the mythical third century Celtic bard ''discovered'' by the Scottish writer James Macpherson in the middle of the eighteenth century, but later condemned as a fraud, is to be resurrected for the first show designed to be exhibited outside Edinburgh.

Ossian: Fragments of Ancient Poetry, a series of 25 new works by Calum Colvin, the acclaimed Scottish artist, will also be the first exhibition at the National Galleries, based in Edinburgh, to have its catalogue translated into Gaelic.

After being shown in Edinburgh, the exhibition will travel in its entirety to galleries in Inverness, Thurso, Wick and Kingussie.

Macpherson, a poet, researcher and writer, published the ballads of Ossian after 1760, and for years he was hailed as the discoverer and translator of the ''Homer of Scotland'', according to the French philosopher Voltaire. The authenticity of his myths, which helped ferment and inspire the Romantic artistic movement, was challenged by literary critics, and they were eventually discredited.

However, Colvin, who works with a variety of media including sculpture, painting, installations and photography, was inspired to resurrect Macpherson's texts by the dubious authenticity of the Ossian myths, and their similarity to the deceptions possible with modern digital photography.

Partly funded by a (pounds) 25,000 Creative Scotland award from the Scottish Arts Council, and after two years of work, Colvin will reveal his work on October 4 at the Scottish National Portrait Gallery.

He said last night: ''Scotland is still embarrassed by Macpherson, in a way its been hushed up, maybe because of all the howls of derision from England, whereas most of the world, especially Europe, was fascinated by Ossian.

''I don't think anyone can really say whether he was real or not: I think he was a King Arthur figure: an archetype of a warrior and a poet which evolved over time.''

Macpherson, a Scottish poet and entrepreneur, born in 1736, found the basis for his Ossian tales in his many travels to Perthshire, Argyll, Inverness and the Western Isles.

However, he was an indifferent speaker of Gaelic, and often relied on translations for his material.

When he first published the works, he claimed the tales, first published in 1761, were the work of Ossian, the son of a third century hero called Fingal.

The tales were at first met with resounding praise across Europe and were welcomed by the cultural elite - the stories inspired Napoleon, Schubert and William Blake, among others.

However, the authenticity of his tales was challenged in both England, by Samuel Johnson, and Ireland. Eventually, after a special commission was set up to judge their authenticity, the gloomy and romantic stories were virtually discredited and have remained largely neglected in modern times.

Later research found that much of the tales were based on genuine Highland traditions, and some of the characters appear in other Gaelic literature - such as Fingal, who is believed to be the same character as the warrior Fionn MacCumhaill.

Colvin, born in Glasgow in 1961, studied at Duncan of Jordanstone College of Art, Dundee, where he is now also a professor, before concentrating on photography, which he studied at the Royal College of Art in London.

One of his main artistic methods is to construct, then paint over, three-dimensional environments in his studio. He then photographs the finished piece, which becomes the final work.

The tour, which is a collaboration between the galleries and Highland Regional Council, is to be followed by others in the future.

James Holloway, director of the Scottish National Portrait Gallery, said: ''We want to do more tours, we feel very strongly that the National Galleries, although they are based in the capital, are more than that. We cannot take all the paintings to everyone, but we can move some of them, some of the time.''

Mr Holloway said that Colvin's work with digital photography, which can distort and subtly change images of reality, is the ideal medium to evoke the myths of Ossian.

He said: ''Ossian is a fascinating figure, and this exhibition asks: What is real? What is false?''

''The way Calum works, his work can be seen like a series of theatrical veils, which reveal different sides to the story - photography is a very appropriate medium for the tales of Ossian.''

An EPIC Pedigree

The Poems of Ossian, first published in 1761 as Fingal: An Ancient Epic Poem, were a cultural sensation.

Napoleon Bonaparte had a copy of the book (his favourite) in his knapsack when he invaded Russia.

In Germany and Scandinavia, princes were named Oscar after a character in the tales.

In Alabama in the US, the city of Selma is named after the palace of the character of Fingal, also honoured by Fingal's Cave, the overture by Felix Mendelssohn.

The Ossian tales gave impetus to the Romantic movement, and also the study of folklore and Celtic languages and custom.

Schubert and Brahms composed pieces inspired by the stories.

In literature, wordsmiths fell under Ossian's spell: William Blake, Henry Thoreau, George Byron, Walter Scott and Matthew Arnold praised or imitated the poetry and prose.

A gravestone, under which Ossian 'lies' in the Sma' Glen, Perthshire, is inscribed with Scott's words: ''In this still glen, remote from men, Sleeps Ossian, in the narrow glen.''