3. DEW PONDS
The Down country of southern England is one of the few places in the world where the people go to the hilltops to seek water in dry weather. On the summits of the Downs are found many artificial shallow ponds, most of them very old. Some, indeed, date back to prehistoric times. The bottom of these ponds consists of a layer of puddled chalk or clay and is impervious to water, so that there is no loss by seepage. As the ponds are not fed by springs or surface drainage, and as lack of rain does not cause them to dry up, it is popularly believed that their maintenance depends upon dew. Hence they are called “dew ponds.”
Kipling mentions them in his poetical description of Sussex:
We have no waters to delight
Our broad and brookless vales—
Only the dew pond on the height
Unfed, that never fails.
The leading authority on dew ponds is Mr. Edward A. Martin, who has written a book about them. Mr. Martin’s experiments have demonstrated that dew can make no important contribution to the water supply of these ponds. The rainfall on the hilltops is somewhat higher than in the valleys, and the greater part of the water in the ponds is undoubtedly derived from this source. The real key to the mystery, however, is found in the wet fogs that drift in from the sea. The process of “fog drip,” which we have mentioned in connection with the rain tree, supplies the deficiencies of the rainfall, and the name “mist ponds,” occasionally applied to these bodies of water, is more appropriate than “dew ponds.”
It remains, however, an interesting paradox that, in time of drought, the farmers of the Downs drive their cattle to the hilltops to be watered and send their carts uphill to procure water for household use in the valleys below. Was it, perhaps, in this topsy-turvy region—where uplands are called “downs”—that Jack and Jill went “up the hill” on their ill-starred water quest?