As this month opens, the time approaches for the now-annual Irish art auctions in London. As a way of encouraging potential buyers, Sotheby's has sent a selection of the work on offer on Thursday, May 21st, on tour. In line with the past couple of years, Jack B. Yeats is particularly well represented, with no less than 21 pictures in the sale. Mark Adams of Sotheby's, who has been responsible for bringing together many of the auction's lots, is particularly pleased with Yeats's Singing `Oh, Had I the Wings of a Swallow', which dates from 1925. Owned by the same Dublin family for the past 50 years and in excellent condition, this is a gloriously high-coloured piece, in which tones of red and yellow predominate.

It depicts a girl breaking into song on a train out of Dublin, and as a mark of the oil's importance, no pre-sale estimate is being given by Sotheby's. The house is clearly hoping a new record for Yeats will be set with this picture. Tralee, another oil by the same artist and dating from a year earlier than the other lot, is a rather darker and more romantic piece, showing a solitary figure sitting on the water's edge while a group of well-dressed figures walk past. This is expected to sell for sterling £250,000-£350,000.

A group of four smaller oils on panel by Yeats, and sharing the same dimensions, are equally charming - particularly The Young Donkey. They carry estimates of between £50,000 and £120,000 each. Drawings, watercolours and cartoons from Yeats are all included in the sale, together with an unusual double portrait of the artist and his brother, William Butler, by Louis Le Brocquy. Dating from 1992, this is believed to be unique by Sotheby's, which has, accordingly, given it a price tag of £30,000-£40,000. Not surprisingly, the auction house is not depending only on Yeats for success in this year's Irish art sale. Among the discoveries is a hitherto-unknown work by Leech, The Pier, Concarneau (£70,000-£100,000), which has been in New Zealand since being given by the artist to one of his friends. Orange and red feature strongly in the picture, dated circa 1908/1909.

Leech's slightly later Children on the Beach with Breakers (£20,000-£30,000) is a dazzling, impressionistic play of sunlight on water. Similarly, his Cat's Paws, Concarneau (£30,000-£40,000) also focuses on the effect of light bouncing off the sea. Two other paintings by different artists are notable, too for their ability to capture strong light: a late Lavery with the self-explanatory title Sunbathers (£50,000-£70,000) and James Humbert Craig's small Jardin de Tuileries, Paris (£6,000-£8,000).

Next week, the Sotheby's selection goes on view in Belfast, where there is likely to be particular interest in the work of a number of Northern Irish artists, such as Daniel O'Neill and Gerard Dillon. One lot in the sale, The Travellers (£10,000-£15,000), was jointly painted by the two artists, although only signed by O'Neill, and the latter's portrait by Dillon (£2,000-£3,000) is a further testament to their long friendship.

Dillon's Girl in a Bedsitter with a Cat (£10,000-£15,000) shows the artist's flat at Abbey Road in London, which he regularly depicted, while Harvest Picnic (£12,000-£16,000) and Girl on a Rug (£20,000-£30,000) are particularly good examples of O'Neill's work.

Northern Irish collectors are likely to be especially interested in a couple of other pictures in this sale: William Conor's Waiting for the Excursion Train (£20,000-£30,000) and an oil by Stanley Spencer. Shillington's House (£70,000-£80,000) shows a well-tended landscape outside Belfast, painted during a visit to the area in 1951. Restrictions of space preclude much further discussion of lots being offered by Sotheby's but among the paintings there are also a number of pieces by Paul Henry, Harry Clarke (a previously unknown watercolour and gouache on silk), Mainie Jellett, Mary Swanzy and, among living artists, Derek Hill and Tony O'Malley.

The auction house, as before, brought over from London a few items of silver but none of the Irish furniture it will be selling. Among the latter group are pieces by Robert Strahan and Co and Mack, Williams and Gibton. There are in addition a number of mahogany tables with classic claw feet. Viewing continues today at Newman House in Dublin from 11 a.m. to 4 p.m.

Singing `Oh, Had I the Wings of a Swallow' by Jack B. Yeats, one of 21 works by the artist to be included in the Sotheby's sale of Irish art on May 21st

Another oil by Jack Yeats, entitled Tralee. It has an estimate of sterling £250,000-£350,000