Tomorrow is the feast of St Bartholomew and in rural Yorkshire, it was known for two things - first, ancient weather lore said that the season's dew arrives on this date and second, it was the occasion for feasts and fairs, one of the survivors being Witton Feast in Wensleydale with its curious Burning of Old Bartle.

First, the dew. Most of us are familiar with the appearance of dew on the grass and cool surfaces, although we are seldom aware of it during the hot summer mornings. As autumn approaches, however, the lawns and verges are covered with a fine layer of moisture, enough to thoroughly soak our shoes and to make us aware of the sheer number of spiders' webs in the hedgerows. So what is dew?

It is moisture which materialises in the form of tiny droplets of water. It settles on plants and objects like car roofs when the earth cools rapidly after the heat of the day.

The autumn combination of high humidity followed by long clear nights is ideal for the production of dew and it appears when the moisture, which is naturally present in the air, condenses to reveal itself on a variety of cool surfaces. This occurs when the air temperature falls until it reaches what is known as the dew point.

If there is a layer of cloud, then this cooling will not occur and dew will not form. The presence of dew therefore means the night has been fine, dry and clear with little wind - and a bonus is that the day which follows will be fine and dry.

There is a piece of old weather lore which says: "With dew before midnight, the next day is sure to be bright" while another adds "If the dew lies plentifully on the grass after a fair day, it is a sign of another," and it was Aristotle who said: "Dew is produced in serene weather and in calm places."

Years ago, people liked to walk barefoot in dew because they thought the pure liquid would cure, or at lease ease, various complaints of the feet, while the more daring would roll naked in the morning dew for similar reasons, often in the belief it would cure skin diseases. May dew was thought especially beneficial, with some ladies thinking it made them more beautiful.

Catherine of Aragon was one such lady and, with 25 of her maids, she would go gathering small phials of dew to store for this very purpose. I am told too, that the farmers of ancient Slavonia would bathe their cows in dew, thinking it helped to keep away witches and evil spirits.

One benefit of dew is that it provides moisture for the landscape when there is no rainfall, and this was recognised years ago by farmers who constructed dew ponds.

In areas where there were no streams or springs, these provided drinking water for the livestock and because these ponds had no outlets or inlets, they never ran dry.

Although the original dew ponds were formed by nature, farmers soon realised they could construct them.

Up to 30 yards in diameter, a dew pond is a saucer-shaped hollow up to six feet deep in the centre. Sometimes called a sheep pond or a clay pond, it can be created by lining the hollow with stones, rubble and straw beneath a covering of clay. When it is full, these ingredients help to keep the water cooler than the ground.

Condensation in the night air helps to maintain the supply of water in a dew pond and the fact that the pond is open to the elements in the summer, means its water is never too dangerously cold to be enjoying by sweating horses.

The fairs and feasts held on St Bartholomew's Day were often known as Bartle Fairs or Bartle Feasts, Bartle apparently being a shortened version of the saint's name.

A gigantic fair used to be held at Smithfield in London while a horse fair, said to be England's oldest, was held at West Ardsley near Wakefield, along with others around the country. One of these was at West Witton in Wensleydale, sometimes called the St Bartholomew's Day Fair, but more locally known as Witton Feast. Now, it is usually held on the Saturday nearest his feast day.

Witton Feast ends with an ancient ceremony called the Burning of Old Bartle and although the village parish council is dedicated to St Bartholomew, it seems unlikely that an effigy of him is burned.

One possibility is that Bartle may be linked to the Giant of Penhill, under whose shadow the village lies, or he might be associated with the sun deity known as Baal.

Yet another theory is that Bartle was a horse thief whose crimes are still remembered and a further possibility is that the ceremony stems from pagan times when the last cut sheaf of corn was thought to contain the corn spirit. It was burnt to destroy the evil of that spirit.

In East Witton's case, the effigy of Bartle is carried in procession, to the accompaniment of a chanted verse, to the outskirts of the village where it is ceremoniously burned.

Updated: 12:04 Thursday, August 23, 2001