420 CRETACEOUS. 



excavations have been made in it to obtain the flints, while other openings have 

 been made simply to afford places of security and refuge, and these latter are 

 known as Deneholes (meaning Den holes, although pronounced and sometimes 

 spelt Dane holes). The Deneholes of Kent and South Essex consist of narrow 

 vertical shafts leading to artificial chambers excavated in the Chalk : their depth 

 varying with the distance of that rock beneath the surface. They are found singly, 

 in groups of twos and threes, or in larger collections of perhaps fifty or sixty pits. 

 In South Essex they abound at East Tilbury, at Hangman's Wood near Grays, 

 and along the course of the Mardyke, near Purfleet ; and in Kent they have been 

 met with at Bexley, south of Dartford, and on Blackheath.^ 



Flint has been used since Paleolithic and Neolithic times for the manufacture of 

 implements and weapons. In the earlier times flints were more often obtained 

 from Gravel-beds, but in Neolithic times shafts were sunk into the Chalk to depths 

 of 20 to 40 feet to obtain Flint, and this was extracted by the aid of picks made of 

 Red Deer's antlers. Pits of this description, which often communicate one with 

 another by underground passages, have been discovered at Grime's Graves near 

 Brandon, in the parish of Weeting, Norfolk,- and also at Cissbury near 

 Worthing, in Sussex.'^ A cave in the chalk at Royston, discovered in 1742, 

 which is reached by a shaft, is considered to be of early British or Romano-British 

 age, and has been occupied as a Temple or Chapel. 



Gun-flints in former times were largely manufactured from the chalk-flints, and 

 are still made at Brandon, and, until recently, at Catton and Whitlingham, near 

 Norwich, for export to Africa. Before the invention of percussion-caps, when 

 the demand for gun-flints was much greater, they were made at Lewisham, 

 Maidstone, Purfleet, Greenhithe, and Northfleet,* and also at Beer Head, in 

 Devonshire. 



The flints derived from the Chalk are largely used for road-mending, and when 

 burnt and ground to powder the material is employed in the manufacture of 

 china, porcelain, and flint-glass. Flints have also been used for building-purposes. 

 Inlaid flint-work in church towers and porches is not uncommon in Norfolk and 

 Suffolk ; and specimens of mosaic work are sometimes to be seen. The Old 

 Bridewell by St. Andrew's Church, Norwich, erected about 1400, is a fine specimen 

 of flint work, according to Blomefield "being esteemed the most curious wall of 

 black flints in all England for its neat work and look, the stones being broken so 

 smooth and joined so well." The faces of these flints are covered with " mastoid " 

 pittings, evidently due to the fact that in the original setting of the flints the 

 workmen gave each one numerous taps with probably a wooden mallet, in order 

 to fix it in position, and the blows induced incipient conchoidal fractures which 

 were afterwards perfected by the action of the weather.^ The term Conchoidal, 

 meaning shell-like, is applied to the fracture of flints, and some other rocks, which 

 often exhibit smooth or ribbed convex fractures resembling a Mactra or some 

 other bivalve Mollusc. Conical fractures are not uncommon with flints : they 

 are spoken of as the ' bulb of percussion.' 



Over large areas of the Wiltshire Chalk there is no durable stone except the 

 scattered ' Sarsens,' consequently the Druidical Temples of Avebury and Stone- 

 henge have suffered pillage. (See sequel.) 



The Chalk is one of the most important sources of water-supply, on account of 

 its wide extent, thickness and absorbent nature, a Chalk country as a rule rapidly 

 drying after rain, as the waters sink away quickly.'' Springs are thrown out at the 



1 T. V. Holmes, Trans. Essex Field Club, iii. 54, iv. part 9; Report Lewisham 

 and Blackheath Assoc. 1881 ; F. C. J. Spurrell and T. V. Holmes, P. Geol. 

 Assoc, vii. 400 ; Buckland, T. G. S. iv. 290. 



- Canon W. Greenwell, Journ. Ethnol. Soc. 1871. 



•^ J. Park Harrison, Journ. Anthrop. Inst. 1878 ; Dixon's Geol. Sussex, ed. 2, 

 p. 96. 



* Dr. J. Mitchell, Edin. New Phil. Journ. 1837, xxii. 36 ; Skertchly, Manu- 

 facture of Gun-flints (Geol. Survey), 1879. 



^ Geol. Norwich (GeoL Survey), p. 30 ; C. B. Rose, P. Geol. Assoc, i. 60. 



^ See Whitaker, Proc Norwich Geol. Soc. i. 277. 



