CHALK. 419 



Turrilites Wiestn, Scaphites cBqualis, Holaster suhglohosiis, and Echino- 

 conus castaneus} (See pp. 321, 401.) 



From the Chalk at Beer Head, near Seaton, Mr. C. J. A. Meyer 

 records, Chalk Marl with Rhynchonella Mantelliana, Ammonites 

 JMantelli, Discoidea cylindrica, D. subuculus ; Lower and Middle 

 Chalk, Tercbratiila carnea, T. semiglobosa, Rhynchonella Cuvieri, 

 Inoceramus mytiloides, I. Brongniarti, I. Cuvieri, Holaster planus, 

 Micraster corbovis ; Upper Chalk, Micj-asier coranguinum? 



In this district the Chalk becomes of additional interest, from 

 the fact that the outlier at Dunscomb Hill, east of Sidmouth, is the 

 most westerly portion of the formation in England ; the extensive 

 beds of flint and chert gravel that cap the Greensand heights of 

 Blackdown and the Haldon Hills, and that descend into the Bovey 

 Valley, however, furnish some records of the former extent of the 

 Upper Cretaceous strata in that direction. 



Economic ptvducts, etc., of the Chalk. 



The Chalk is extensively burnt for lime, by which process it loses about half its 

 weight in carbonic acid. The lime is employed for manuring land, and mixed 

 with sand it forms mortar. Chalk is also manufactured into whiting at Grays, 

 Northfleet, Kintbury (between Hungerford and Newbury), Hartford Bridges, near 

 Norwich, Flessle, and other places. The whiting is prepared by grinding the 

 Chalk to a fine pulp with water, and allowing the whole to flow into a series 

 of tanks ; the sediment is then formed into cakes and dried. By the addition of 

 linseed oil a form of putty is also made from this sediment. Chalk, mixed with 

 clay (such as Gault or Boulder Clay) or with river-mud, is burnt and manufactured 

 into Portland or Roman cement at Northfleet, Rochester, Dovercourt, Arlesey 

 near Hitchin, Burgh Castle near Yarmouth, etc. Mixed with gum arabic and a 

 little glycerine, it forms a good cement for mending fossils. 



Hard beds of Chalk, as previously mentioned, have been employed for building- 

 stone, notably the Beer Stone of Devonshire. In Lincolnshire hard chalk w^as 

 used in the construction of Louth Abbey, and in Norfolk beds have been similarly 

 employed, although chiefly for inside work. The important Coprolite-beds found 

 in many places at the base of the Chalk have been already described. (See 

 pp. 410, 416.) 



Many Chalk or * Marl ' pits, known as Cealc-seathas, were opened in Saxon 

 times. (See p. 242.) At the present day pits are occasionally opened to a depth 

 of upwards of 100 feet ; and the men work at the top with levers and throw down 

 the Chalk in great masses. Blasting is occasionally resorted to ; and a remarkable 

 blowing up of Chalk took place many years ago at the Round Down Cliff, Dover, 

 when hundreds of tons were thrown into the sea to make an opening for the 

 railway beneath the cliff. The Chalk is sometimes worked by means of tunnels 

 or galleries driven into the hill-slopes, a plan less frequently adopted now than 

 formerly, although the object was to avoid the removal of superincumbent beds of 

 gravel, etc., known in Norfolk as ' Uncallow.' Near Norwich many of these 

 subterranean workings remain, and, as at Stone Hills, on the Dereham road, they 

 extend a considerable distance, branching in various directions ; the passages are 

 not less than six feet in height and six feet in width, and sometimes more lofty. 

 There are similar Chalk caves at Camden Park, near Chiselhurst. 



Not only has Chalk itself been worked for various purposes, but extensive 



' Geol. E. Somerset (Geol. Survey), p. 141. See also J. Wiest in Davidson's 

 Brit. Cretaceous Brachiopoda, p. 114. 

 2 Q. J. XXX. 371, 393, 



