The examination of waters and water supplies / by John C. Thresh.

  • Thresh, John C. (John Clough), 1850-1932.
Date:
1904
Catalogue details

Licence: Public Domain Mark

Credit: The examination of waters and water supplies / by John C. Thresh. Source: Wellcome Collection.

    29/500 (page 9)
    The Lower Oolite is separated from the Middle Oolite by the Oxford clay, which varies in thickness from 300 to 600 feet. This clay contains calcium carbonate and iron sulphide (pyrites). The Great Oolite (Lincolnshire, Northamptonshire, Gloucestershire, and Oxfordshire) is from 250 to 300 feet in thickness and consists of beds of shelly limestone and marly clay. Within the Thames Basin they have a collecting area of about 300 square miles, and give rise to numerous fine springs. The water is usually thrown out by the outcrop of Fuller’s earth. Below the Fuller’s earth is a series of beds, the most important of which is the Lincolnshire Oolite, which, in that county, attains a thickness of 200 feet. It thins out towards Kettering. This inferior oolite and underlying sands are about 320 feet thick in the neighbourhood of Cheltenham, and thin off, to disappear under Oxfordshire. It follows, there¬ fore, that a good deal of water is imprisoned in these strata, although springs of considerable volume are common at the base of the hills of this formation. The water naturally con¬ tains much calcium carbonate, and in all respects resembles water from the superficial chalk. Where the water is im¬ prisoned, however, it undergoes an entire change of character, becoming alkaline, now resembling the water from the deep chalk of Essex and London. (98-108.) The oolite probably rivals the chalk as a source of water supply, both in quality and quantity. There is greater danger, however, of polluting matter being carried long distances, as from the compact character of the limestone the water can only travel through and accumulate in its fissures. The Lias ‘ forms a conspicuous band stretching across England from Whitby and Bedcar, on the coast of Yorkshire, to Lyme Begis, on the coast of Dorset, the harder rocks forming gentle escarpments which overlook the vales formed in the softer or clayey strata ’ (Woodward). It consists of beds of clay, shale, limestone, and marlstone. In certain districts this formation yields a considerable quantity of water, and springs of large volume are not infrequent. The water is