The general deficiency of moisture characteristic of these chalk hills is such that it is said agriculture flourishes best upon them in what is called a `dropping' summer, when there is a shower every two or three days, the soil absorbing it so quickly. For the grass and hay crops down below in the vale, and for the arable fields there with a stiff heavy soil, on the other hand, a certain amount of dry weather is desirable, else the plough cannot work in its seasons nor the crops ripen or the harvest be garnered in. So that the old saying was that in a drought the vale had to feed the hill, and in a wet year the hill had to feed the vale: which remains true to a considerable extent, so far at least as the cattle are concerned, and was probably true of men and their food also before the importation of corn in such immense quantities placed both alike free from anxiety on that account. This deficiency of moisture being borne in mind, it is a little curious to find ponds of water on the very summit of the down. Scarcely a quarter of a mile from the earthwork, and on a level with it--close to the clump of firs and beech alluded to previously--there may be seen on this warm summer day a broad, circular, pan-like depression partially filled with water. Being on the very top of the ridge, and only so far sunk as to hold a sufficient quantity, there is little or no watershed to drain into the pond; neither is there a spring or any other apparent source of supply. It would naturally be imagined that in this exposed position, even if filled to the brim by heavy storms of rain, a week of sultry sunshine would evaporate it to the last drop; instead of which, excepting, of course, unusually protracted spells of dry weather such as only come at lengthy intervals, there will always be found some water here; even under the blazing sunshine a shallow pool remains, and in ordinary times the circular basin is half full.