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 much softer and really pure spring water. It comes in pipes by gravitation, so there is no expense of pumping; but it was difficult to get recalcitrant ratepayers to lay the water on from the mains to their houses, as that part of the cost had to be borne by them individually; and, before compulsion could be resorted to, the Council had to prove contamination of the wells and close them. To get the evidence samples were submitted to a London analyst, and they were invariably condemned. One of the Councillors suggested sending, with a number of well samples, a sample of the new supply "for a fad." The samples were numbered, but had no other distinguishing mark, and in due course the usual condemnations were received, including that of the new town supply!