164 On the Idenllly of S'llex and Oxygen. 



it ceases entirely to appear in its original state. Every thing 

 connected with the progress of animal and vegetable exist- 

 ence ; with the inscrutable secrets of the assimilating powers; 

 or with the physiology of all organized matter, shows, that 

 transmutation is an operation which we cannot disprove, 

 though we may not be able to trace it through all its steps. 

 As far as concerns the formation of chalk from, silex, the 

 next advance, if there be any such graduation, is most pro- 

 bably into clav; for, we may remark, in all chalky soils, 

 particularlv in such as prevail in the counties of Kent and 

 Sussex, and other parts of England, where the superficial 

 stratum of soil is extremely shallow, that this stratum consists 

 chiefly of argillaceous earth, which, like all other clays, con- 

 tains a considerable quantity of silex in the condiljon ot sand. 

 So prevalent is this mixture of sand in clay, that there never 

 was a specimen of porcelain clay, or of any other species 

 whatever, that did not include a portion of siliceous matter; 

 and the most useful clays, those employed for china and pot- 

 tery in general, seldom contain less than 50 per centum of 

 silex. 



The power of silex as an oxidizing, saturating and neu- 

 tralizing ae;cnt, is by no means confined to rocks, moun- 

 tains, and other inanimate parts of created matter, but it 

 pervades, also as an essential element, the structure of all or- 

 ganized beings, and occupies a distinguished place both in 

 the animal and vegetable ceconomy. '' Nothing is more 

 astonishing," savs Dr. Smith, " than the secretion of flinty 

 earth by plants" — and this is a fact that " is well ascer- 

 tained*." 



That this most dense and insoluble substance is truly se- 

 creted by the peculiar assimilating faculty of the vegetable 

 alone, and never imbibed from the soil by direct absorption, 

 seems certainly to be the more feasible theory ; indeed it is 

 substantiated by experiments and accords with reason and 

 general facts. 



It is truly remarkable, that in those vegetables, where 

 eilcx is most abundant, the chief residence is usually in the 



* Introduction to Botany. 



epidermis 



