Coln enters the county of Middlesex, has a total dip of about 350 feet, or from the higher ground in Bedfordshire of 650 feet, which latter point is about 770 feet above the level of the sea. The highest ground on the ridges between the rivers is capped with portions of the plastic clay in situ, which may be deemed outlying patches of the clay-district, in some cases covered with gravel to a sufficient depth to retain the water to serve the ordinary wants of villages or hamlets, such as Abbots Langley and Bedmont. Thus the population is found either on the ridge or in the valleys near the rivers, the intermediate parts being dependent on water drawn from deep wells sunk into the chalk.
On the accompanying section (see next page), taken on the ridge midway between the rivers Gade and Ver, is shown the depth at which water is found, with its noted alternations at two periods in the same year. The level of the course of the river Gade, with which that of the Ver is nearly identical, is also given between these points. The surface of the subterranean water would be shown by an inclined line, fixed at the river, and more or less elevated or depressed towards the ridge according as the stock of water is augmented by the replenishment of the chalk stratum, or reduced by the natural drainage. Thus in chalk districts the level at which water is found may be accurately ascertained.
The intermediate space between the ridges, and the rivers which run in the valleys, is covered with gravel, often presenting a surface which consists almost entirely of flint-stones, the removal of which, if it were possible, would rather detract from, than add to the productiveness of the soil by quickening evaporation. This soil with slight variations forms the main staple of the district which lies between the outcrop of the London and Plastic clays and the northern limits of the county.
A stranger acquainted with those Western counties which have a soil almost identical with this in its texture and its geological bearings, is here struck by the absence of breeding flocks, the deficiency of stock, the inadequacy of the farm-buildings, and the small size of the enclosures which here prevail. He would find the land cleared of its sheep after the consumption of the swede and root-crop, the hay and straw very generally sold, and barely replaced by London manure, when it is to be had. Very many exceptions may of course be found, among which a farm at Wheathampstead, near the centre of the district under consideration, is a notable instance.
Sheep Farm at Wheathampstead.
The farm consists of 317 acres, of which 20 are in not very productive grass-land. Fifty-six acres of the arable are upon the strong loam of the higher levels, and the remainder is of a lighter
