EDINBURGH (REUTERS).- Staff at a castle in Scotland have discovered a rare letter including the first draft of a poem by Robert Burns 222 years after he posted it.

The letter -- which includes a draft of "On Seeing a Wounded Hare" -- surfaced at Floors Castle in the Scottish borders on the eve of celebrations marking the birth of Scotland's national bard on January 25, 1759.

The letter, dated May 13, 1789, was addressed to James Gregory, then head of Edinburgh University's medical school. It was spotted by a member of the castle staff in an album that had come into the possession of the then 6th Duke of Roxburghe.

The poet sent the letter from Ellisdale, his farm near Dumfries in southwest Scotland, and enclosed an early version of his poem on the wounded hare. Burns expressed his gratitude to Gregory for his support and invited his comments and criticism, asking him to "mark faulty lines with your pencil."

The published poem, On Seeing a Wounded Hare, first printed in 1793, curses the hunter who had shot an animal which limped past Burns in a field:
"Inhuman man! Curse on thy barbarous art,

And blasted be thy murder-aiming eye "

The current 10th Duke of Roxburghe sought expert advice on the letter's authenticity.

It was verified by Iain Gordon Brown, principal curator of manuscripts at the National Museum of Scotland in Edinburgh, David Purdie, editor-in-chief of the Burns Encyclopaedia, and Gerard Carruthers, director of the center for Robert Burns Studies at Glasgow University.

Brown told Reuters that Gregory had probably passed on the letter to a friend, poet and noted London hostess Mrs John Hunter, wife of an eminent surgeon and anatomist, and it had likely come into the Duke's possession from her family.
Purdie said unpublished letters by Burns were extremely rare.

"this example is doubly interesting as it not only displays the evolution of one of his poems, The Wounded Hare, but, in Burns and Gregory, it brings together major figures of both the literary and scientific components of the Enlightenment," he said.

(Editing by Paul Casciato)