DOMAIN III. ARGILLACEOUS. 



coarser sort at Ryegate, which contains crystals 

 of barytes, is of a reddish brown, and is not used 

 in commerce. 



The analysis by Bergman bears that the 

 fullers' earth comes from Hampshire, a mistake 

 followed by a hundred mineralogic writers; and 

 it was probably from Reading, in Berkshire, for 

 in the vicinity of that town there are remarkable 

 quarries, which lie under beds of sea sand, 

 mingled with numerous shells of oysters. It is 

 also found near Woburn, in Bedfordshire, and 

 Ryegate, in Surry. 



Da Costa informs us, that fullers' earth is dug 

 at Wavendon, near Woburn, in Bedfordshire. 

 For about six yards there are layers of reddish 

 sand, then a thin stratum of sand-stone, then 

 sand again for seven or eight yards; after which 

 fullers' earth appears for about eight feet, fol- 

 lowed by sand-stone and sand. At Ryegate 

 and Nutfield, in Surry, the strata are similar; 

 but at Detling, near Maidstone, in Kent, it un- 

 derlies a sandy loam, mixed with a great variety 

 of shells. It is prevented from being exported 

 by a special act of parliament*. 



Near Reading oyster-shells are found at the 

 bottom of a high hill, a hundred feet below the 



* Nat. Hist, of Fossils, 1757, 4to. p. 69. 



