The numerous brooks in the Vale of Evesham supply ample water for the
stock, but in more elevated parts, especially on the chalk Downs of
Sussex, Hants, Wilts, and Dorset, provision is made for an artificial
water supply by what are called "dewponds." A shallow saucer-shaped
depression is dug out on the open Down, the bottom being made
water-tight by puddling with a well-rammed layer of impervious clay.
The first heavy rainfall fills the pond, and, the water being colder
than the air, the dew or mist condenses on its surface sufficiently,
in ordinary weather, to maintain the supply. In a dry time the sheep
can always reach the water, the pond having no banks, by the shelving
formation of the bottom. Sometimes a few trees are allowed to grow
round it; they also act as condensers, and their drip helps to fill
the pond. It is only in an abnormal drought that these dewponds really
fail, and a thunderstorm, followed by ordinary weather, will soon
refill them. Gilbert White, in _The Natural History of Selborne_,
refers to these ponds in a very interesting letter on the subject,
including details of condensation by trees, in which he gives an
instance of a particular pond, high up on the Down, 300 feet above his
house, and situated in such a position that it was impossible for it
to receive any water from springs or drainage, which "though never
above three feet deep in the middle, and not more than thirty feet in
diameter, and containing, perhaps, not more than two or three hundred
hogsheads of water, yet never is known to fail, though it affords
drink for three hundred or four hundred sheep, and for at least twenty
head of large cattle besides."

The natural well-water in the Vale of Evesham is exceedingly hard, and
in the town and some villages was formerly much contaminated. After
great opposition from obstructive ratepayers, a splendid supply was
obtained from the Cotswolds above Broadway, about six miles away, of