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with a large number of other stone implements and flakes. At first sight it seems 

 somewhat curious that these objects of antiquity should still be resting on the 

 surface of the grass, and nestling amongst the common plants of chalky downs. 

 The surface-soil where this flint was found varies from an inch or two to a foot or 

 more in thickness, and one would imagine that in a minimum number of years, 

 amounting to 3,000, the decomposition of the plants, the action of worms and their 

 casts, as described by Mr. Darwin, and the dung of birds and other animals, would 

 ere this have effectually covered flints of the size figured from sight, but such is 

 not the case. 



I have found many worked flints on the Chiltern Hills, resting on the 

 surface of the ground where the earth had been thrown out in pre-historic times for 

 the formation of huts. When flints are first taken from the chalk, they are 

 encrusted with a white external stratum which is due to the decomposition of the 

 flint, the decomposition taking place from the outside inwards ; if a flint is freshly 

 broken it shows a black or coloured internal mass, which will in its turn, at length 

 beccmie white and porcellaneous by the decomposition of the surface, i.e., if the 

 flint is kept in the air or in a porous soil. All the worked flints on the Sussex 

 downs are white from their many long 3'ears of exposure. In the accompanying 

 illustration, the left hand figure shows the front and worked face of a flint, 

 probably used in pre-historic times for scraping the skins of animals : the right 

 hand figure shows one edge of the implement, and the lower figure its transverse 

 section ; the back is un worked, i.e., perfectly plain. Many of the worked flints 

 near Eastbourne show part of the original crust of the flint, as the one does now 

 under description. When our implement was in process of manufacture, the 

 flakes struck from the face for some reason fell short and stopped suddenly at the 

 point A, leaving a piece of the original decomposed crust, which is clearly seen on 

 the section at B, and also seen covered with lichens on the front and side view, F G. 

 How long this thickness of crust required for its formation whilst the flint was still 

 in the chalk it is impossible to say, but the time that has passed since the flint was 

 first worked has been sufficient for the formation of a second and much thinner 

 white porous and porcellaneous crust, as seen at C C in the section. On a freshly 

 fractured flint it is probable that no vegetable life of any sort could exist, but as 

 soon as the surface becomes roughened and abraded by the weather, as on old win- 

 dow glass, vegetable life of a low order gains a footing, and more or less hastens 

 the decomposition. So absorbent of moisture are some old and decomposed flint 

 flakes, that they will weigh one-twelfth more after being placed in water, than 

 when in a dry state. This slight retention of water is sufficient to support a few 

 unicellular algae, and other plants of a low order. Growing on our Sussex Downs 

 flint, there are no less than four lichens. The surface which has been worked is 

 not yet sufficiently decomposed to support fully developed (lichens, the black 

 patches at D therefore, belonging to Verrucaria nigrescens, are invariably sterile, 

 as are the sma,\l olivaceoics pustules at E, which belong to the rudimentary condition 

 only of Lecanora gibbusa. On the piece of original crust, however, and where 

 more water is retained, the moisture enables Lecanora parella at F F to grow with 



