A SUNDIAL is to be unveiled in the grounds of the Bowes Museum to commemorate the Queen Mother's 40-year patronage of the Barnard Castle treasure house.

Commissioned by the museum Friends following a suggestion from committee member Brian Parkinson, the armillary sphere will be mounted on a plinth provided by Dunhouse Quarry at Staindrop, where the stone used to build the museum originated. The sphere, 80cm in diameter, has been fashioned from marine grade surgical steel by Oxfordshire sculptor David Harber.

An armillary sphere typically consists of a mounting ring engraved with the eight cardinal points of the compass, and a series of concentric rings which represent the circles of the celestial sphere. The shadow is cast by a rod passing through the centre of the sphere, parallel to the polar axis. The dial is set to the latitude of its resting place, so in this case it will only be accurate when in place in Barnard Castle.

The Friends have agreed the following inscription: "This armillary sphere has been placed here by the Friends of the Bowes Museum in memory of HM Queen Elizabeth the Queen Mother (1900-2002) who was their patron for forty years." It also contains the words "Hora Transit Manet Amicitia" which means "The hour passeth, friendship endureth".

Friends' chairman Lesley Taylor is delighted with the sundial: "Siting it in the grounds will give free access and hopefully pleasure to everyone."

Information will also be included about the distances to several of Her Majesty's former homes including Glamis Castle, Clarence House and Streatlam Castle.

Although the actual structure will be completed in about four weeks' time, installation and landscaping will then have to be undertaken. The Friends are toying with the idea of inviting a member of the royal family to officially unveil the sculpture in 2005.

The sphere will be positioned on the left hand side of the museum's entrance drive, on the ridge near the rear of the Catholic church, and will be approached by a path bordered by lavender.