358 Dr. Mitchell oti the Beds immediately above 



flints afforded the best sort of gun-flints for gentlemen's fowl- 

 ing-pieces; but being less easily made than the gun-flints 

 from ihe challc flints, and the material being less abundant, 

 they were more expensive. On account of the presence of so 

 much iron they are totally useless in the porcelain manufac- 

 ture ; but I have been informed that on one occasion as many 

 as ten tons were obtained at the bottom of the great pit at 

 Erith which were so pure as to be saleable for that purpose. 

 Few specimens are large enough for building, and therefore 

 their chief use is for road-material. 



An irregular broken line of flints of this description is to 

 be seen at the sides of the deep cuttings at the entrance of 

 the tunnel of the London and Birmingham railway beyond 

 Watford. Great diluvial action has taken place, and the 

 upper surface of the chalk is torn and ridged ; and if, as we 

 have no reason to disbelieve, there was a bed of sand here 

 over the chalk, we must in consequence suppose that it has 

 all been carried away. But the flints peculiar to such beds 

 are seen above the solid chalk, and below the diluvial matter, 

 scattered along on both sides of the cutting. 



I have seen such flints in considerable quantity in the fields 

 on the east side of Margate, in the Isle of Tlianet, and like- 

 wise in Norfolk and Suffolk. 



In the pit on the south side of Elmstead near Chiselhurst, 

 and in the pit on the south side of the Woolwich road, there 

 are in the same beds with these flints innumerable small frag- 

 ments of the same kind of flint, but not in the least rounded, 

 and with sharp edges ; which proves that in these localities 

 there had been agitations, and that the flints had readily been 

 broken into fragments. 



The .most extensive section of this stratum which I have 

 ever seen is at Newhaven in Sussex. It extends upwards of 

 a mile along the top of the cliff, and the peculiar flints may 

 be collected all along the foot of the cliff. They are well 

 known to the fishermen who collect chalk-flint boulders for 

 the Staffordshire potteries, and are carefully avoided. One 

 of these men said to me that he knew that one of them would 

 be enough to spoil a hundred pounds' worth of good material. 

 I found a cast of an Echinus there, but not a particle of the 

 shell remained upon it. 



There is another and very distinct variety of flint, which 

 may be seen in some of the pits in the same bed in which 

 the preceding variety has been found. I may mention the 

 pit at old Charlton near the Woolwich road, in the trenches 

 dug by Mr, Rosier near Gravesend, and on the south side of 

 Elmstead near Chiselhurst; also at Purfleet. 



