GEOLOGY 



MALM OR TUFA. In the valley of the Kennet there are a few 

 small patches of a calcareous loam. They rest upon peat or alluvium. 



One patch near Newbury has been described as full of shells of 

 land and freshwater mollusca and caddis-worm cases. Many of them 

 were coated with concretionary carbonate of lime. It is a flood water 

 deposit. In a well already mentioned it was found to be 6 feet thick. 1 



GREYWETHERS OR SARSEN STONES 



The greywethers have long attracted attention. They are de- 

 scribed in Lyson's Magna Britannia as ' those remarkable stones, called by 

 the country people sarsden stones or the greywethers, which are scat- 

 tered over the Downs. They appear to have been removed by some 

 violent concussion of the earth, as they evidently lie on strata to which 

 they do not naturally belong. The greatest number of them are to 

 be seen in a valley near Ashdown Park on a stratum of chalk, others 

 on a bed of clay in the parish of Compton Beauchamp. They are 

 frequently blasted with gunpowder and used for pitching, etc., but are 

 too hard to be worked.' * 



The ' Blowing Stone ' on the road from Faringdon to Uffington 

 was described by Mr. James Sowerby in a communication to the 

 Linnsean Society on November 7, 1809." 



Mr. Aveline remarks that around Middle farm, Knighton Bushes, 

 Weathercock Hill and Hone Warren they are plentiful, and he gives 

 the dimensions of a number of stones, the largest measuring 8 feet by 

 8 1 feet by 5 feet, 9 feet by 5 feet by 2 feet, and 12 feet by 6 feet by i 

 foot. 4 Similar stones occur on the east of the county on Bagshot 

 Heath, etc. 



These stones are believed to be derived from the Reading and 

 Bagshot Beds and possibly in some cases from the basement bed of the 

 London Clay. They are usually formed of hard, often very hard, sand- 

 stone or quartzite, and sometimes have a somewhat cherty appearance. 

 Their minute structure, according to Professor Judd, varies greatly. 

 Those with saccharoid fracture stand at one end of the series. An 

 example from Camberley in Surrey is wholly made up of sand grains, 

 and much of the cement is ferruginous. 



At the other end of the series stand sarsens with a fracture like 

 some cherts. He mentions one case where the original sand grains had 

 almost wholly disappeared and an aggregate of grains of secondary quartz 

 had been formed. 6 



Mr. Hudleston has described this class of stone as siliceous doggers 

 or concretionary slabs which have hardened in situ and have resisted the 

 atmospheric agencies of destruction, and after noting specimens which 



1 Prof. Geol. Assoc. (1879-80), vi. 188 ; see also a paper by A. S. Kennard and B. B. Woodward, 

 op. cit. (1901-2), xvii. 213. 



8 Lysons, Magna Britannia (1806), i. 192. s Trans. Lin. Soc. x. 405. 



4 'Geology of Parts of Oxford and Berks,' Geol. Survey (1861), p. 47. 

 6 Geological Mag. (1901), p. i. 



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