GEOLOGY are used not only for building hovels with the aid of a mortar of moist clay, but they are used with advantage in dwelling houses, as when faced with bricks the thick walls make a dry house, cool in summer and warm in winter. The stones in the Boulder Clay are sometimes used for road- mending in areas where gravel is scarce. The presence of lignite or bituminous shale in the Boulder Clay has led at times to fruitless searches for coal, as near Framingham Pigot. Water is sometimes obtained from sandy and gravelly seams and beds in the Boulder Clay, and occasionally it is of an artesian character, being pent up beneath the clayey drift. A petrifying spring, deriving its calcareous matter from the Chalky Boulder Clay, occurs at Burgh Apton, and a mineral water has been advertised as the Shelfanger Spa, near Diss. The more clayey varieties of the Chalky Boulder Clay form the heavier lands of Norfolk ; the strong loam or 'clay marie ' of Hethel, Mulbarton, Long Stratton, Pulham and Tivetshall (where the clay is from 50 to 90 feet thick). Beans and wheat are cultivated with advantage, while primroses flourish in the banks and line the ditches. Much of the country has a park-like aspect owing to the strong well-timbered hedgerows, the broad strips of grass land which border the roads, and the numerous greens and commons. It is by no means easy to separate the gravels and sands known as Plateau Gravels from the sands and occasional gravels which underlie the Boulder Clay, and have been termed Middle Glacial. The two groups come together near Cromer in the sand and gravel hills which extend from Paston to Weybourne and Holt, where they form a bold and picturesque range of hills bordering the sea. Here the coarser upper gravel cuts into the lower sands in places. They form the wooded ground, occupied mostly by fir plantations at Felthorpe and Horsford ; and in West Norfolk they constitute heathy tracts, rabbit-warrens, and sheep-walks. Some of the gravels contain large rounded flints about the size of old-fashioned cannon balls, and were termed ' cannon-shot gravels ' by S. V. Wood, jun. These are the gravels which have been extensively dug on Mousehold, and were formerly used for paving streets in Norwich where they are still known as cobbles or ' petrified kidneys.' Occasional Paramoudras occur in these gravels, and they contain many flint-casts and moulds of Chalk fossils. The boulder-gravels occur at Poringland and Strumpshaw, at Tharston Furze Hill, Hapton and Wymondham, at North Elmham, Tatterset, Hempton Common near Fakenham, Syderstone and Docking. Near Docking the gravel contains hard chalk as well as flint, and blocks of it cemented by iron-oxide have locally been used for building. In many of the localities the flint boulders have been used for building- purposes. The round church towers of Norfolk were mostly built of such materials, there being little or no freestone in the county suitable for corner-stones. These coarse gravels probably resulted from the melting of the ice which brought the materials of the Chalky Boulder Clay. The gravels 21
