GEOLOGY Chater and Gwash, especially in their lower reaches, for a few miles above their respective junctions with the Welland. At the period when these gravels were formed the Fenland was a bay of the sea, and the estuary of the Welland came up to the point where it is joined by the Gwash. This estuary was gradually choked with gravel and sand, a great plain of which now extends eastward to Deeping and Peakirk. The river gravels probably contain mammalian bones and fresh- water shells, but both seem rare in Rutland and no record of any has yet been published. ALLUVIUM Of this, the newest deposit in the county, Professor Judd writes as follows : — The flat bottoms of the valleys of the existing rivers are covered with a fine black loam or silt which is still in process of formation, a constant accession to, and redistribution of, its material taking place as the result of ordinary river action. This loam is often crowded with the shells of those molluscs which live on terrestrial surfaces or in marshes. . . . The flats formed by these alluvial deposits (which are conspicuous in the valley of the Welland and the Gwash) are during the winter season for the most part under water ; they are distinguished for their great fertility and constitute most admirable grazing lands. WATER SUPPLY The supply of pure water is a matter of prime importance to the population both of towns and of country places, and as most running streams are more or less polluted a few miles below their sources, and as springs are not always conveniently near, new wells and borings are continually being made. The existence of springs and the success of boring for water are both dependent upon the geological structure of the district, and consequently a few remarks on the subject of water supply will not be out of place in this article. In the county of Rutland the two great sources of supply are the Lias Marlstone and the Inferior Oolite, the latter comprising the North- ampton Sand and the Lincolnshire Limestone. The Marlstone is the chief source of supply in the north-western part of the county ; thus Oakham has always derived its supply from springs issuing from this rock. Its modern waterworks also take their water from the same source, but the supply comes from springs at Braunston, in the valley of the Gwash, about two miles south-west of Oakham. Mr. Fox-Strangways informs me that these springs are now tapped by a boring 40 feet in depth, which traverses first a deposit of white tufa, then 1 5 feet of Upper Lias Clay and about the same thickness of Marlstone-rock. The Inferior Oolite however is a much more important source, inasmuch as it includes a thickness of from 80 to 120 feet of permeable strata and consequently holds a much larger quantity of water ; more- over it is available not only over the greater part of Rutland but over those parts of Lincolnshire and Northamptonshire which lie to the east- » 'The Geology of Rutland,' Mem. Geo/. Survey, p. 253 (1875). 13
