The chalk can be traced in England from Flamborough Head in Yorkshire, in a south-westerly direction, to the coast of Dorset; and it not only underlies the whole of the S.E. corner, where it is often obscured by Tertiary deposits, but it can be followed across the Channel into northern France. Rocks of the same age as the chalk are widespread (see [Cretaceous System]); but the variety of limestone properly called by this name is almost confined to the Anglo-Parisian basin. Some chalk occurs in the great Cretaceous deposits of Russia, and in Kansas, Iowa, Nebraska and S. Dakota in the United States. Hard white chalk occurs in Ireland in Antrim, and on the opposite shore of Scotland in Mull and Morven.
Economic Products of the Chalk.—Common chalk has been frequently used for rough building purposes, but the more important building stones are “Beer stone,” from Beer Head in Devonshire, “Sutton stone” from a little north of Beer, and the “Totternhoe stone.” It is burned for lime, and when mixed with some form of clay is used for the manufacture of cement; chalk marl has been used alone for this purpose. As a manure, it has been much used as a dressing for clayey land. Flints from the chalk are used for road metal and concrete, and have been employed in building as a facing for walls. Phosphatic nodules for manure have been worked from the chloritic marl and Cambridge Greensand, and to some extent from the Middle Chalk. The same material is worked at Ciply in Belgium and Picardy in France. Chalk is employed in the manufacture of carbonate of soda, in the preparation of carbon dioxide, and in many other chemical processes; also for making paints, crayons and tooth-powder. Whiting or Spanish white, used to polish glass and metal, is purified chalk prepared by triturating common chalk with a large quantity of water, which is then decanted and allowed to deposit the finely-divided particles it holds in suspension.
Chalk Scenery.—Where exposed at the surface, chalk produces rounded, smooth, grass-covered hills as in the Downs of southern England and the Wolds of Yorkshire and Lincolnshire. The hills are often intersected by clean-cut dry valleys. It forms fine cliffs on the coast of Kent, Yorkshire and Devonshire.
Chalk is employed medicinally as a very mild astringent either alone or more usually with other astringents. It is more often used, however, for a purely mechanical action, as in the preparation hydrargyrum cum creta. As an antacid its use has been replaced by other drugs.
Black chalk or drawing slate is a soft carbonaceous schist, which gives a black streak, so that it can be used for drawing or writing. Brown chalk is a kind of umber. Red chalk or reddle is an impure earthy variety of haematite. French chalk is a soft variety of steatite, a hydrated magnesium silicate.
The most comprehensive account of the British chalk is contained in the Memoirs of the Geological Survey of the United Kingdom, “The Cretaceous Rocks of Britain,” vol. ii. 1903, vol. iii. 1904 (with bibliography), by Jukes-Browne and Hill. See also “The White Chalk of the English Coast,” several papers in the Proceedings of the Geologists’ Association, London, (1) Kent and Sussex, xvi. 1900, (2) Dorset, xvii., 1901, (3) Devon, xviii., 1903, (4) Yorkshire, xviii., 1904.
(J. A. H.)
CHALKHILL, JOHN (fl. 1600?), English poet. Two songs by him are included in Izaak Walton’s Compleat Angler, and in 1683 appeared “Thealma and Clearchus. A Pastoral History in smooth and easie Verse. Written long since by John Chalkhill, Esq., an Acquaintant and Friend of Edmund Spencer” (1683), with a preface written five years earlier by Walton. Another poem, “Alcilia, Philoparthens Loving Follie” (1595, reprinted in vol. x. of the Jahrbuch des deutschen Shakespeare-Vereins), was at one time attributed to him. Nothing further is known of the poet, but a person of his name occurs as one of the coroners for Middlesex in the later years of Queen Elizabeth’s reign. Professor Saintsbury, who included Thealma and Clearchus in vol. ii. of his Minor Poets of the Caroline Period (Oxford, 1906), points out a marked resemblance between his work and that of William Chamberlayne.