The Triassic strata which form the country surrounding Birmingham consist of the usual divisions of sandstone and marl; the sandstones predominating below, the marls above. In the immediate neighbourhood of the town, the sandy beds are divided from the marly or clayey strata by a dislocation or line of fault which runs from north-east to south-west, taking a line from Erdington to Rubery, and traceable altogether for a distance of about twenty miles. The fault runs through the town of Birmingham nearly parallel to the River Rea, and from a quarter to half a mile west of the present bed of the river. The Lower Keuper sandstone, which forms a surface band one to two miles in width on the west of this fault, is a porous stratum about 200 feet in thickness. It is underlain by the Bunter Pebble Beds, 300 to 400 feet in thickness, which crop out further to the west, andwhich contain an inexhaustible supply of water. From three deep wells in the suburbs of Birmingham —two on the north at Perry and Witton, and one on the south near Selly Oak—the Corporation Waterworks obtain daily a supply of over eight million gallons of water, most of which comes from the Pebble Beds, which occupy the lower portion of each well or bore-hole. The water is of good quality, showing from nine to fifteen degrees of hardness.