l66 On the Identity of Silex aiid Oxygen. 



probably in the state^of sub-carbonate. By burning a straw 

 with the blue flame from the blow-pipe, beginning at one 

 end of the straw, this was converted into a fine pellucid 

 globule of glass, almost fit for microscopic experiments. It 

 was also suggested, that flint in these hollow bodies might be 

 considered as analogous to tiie earth of bones in animals. 

 By giving firmness and tenacity to the vegetable structure, 

 it may assuredly serve this purpose, but I suspect it is pre- 

 sent for other intentions, and that it contributes to the 

 foroiation of certain immediate materials in the organiza- ' 

 tion. 



It is, probably, from the same siliceous principle that straw 

 forms the basis of some of the richest manures, and not on 

 account of its carbon only 3 for saw-dust and many other 

 liiZneous bodies, which contain more carbon, prove to be 

 inferior or useless. The straw of oats, particularly, is burned 

 and the ashes are employed to polish marble, and this must 

 consequently arise from the silex, of which about one half 

 of the ashes chiefly consist ; for according to M. Vauque- 

 lin's analysis, in 100 parts, there are 55 of silex besides 

 other matters *. 



In no case whatever does it appear that silex can be con- 

 sidered as a fortuitous ingredient in the ceconomy of vege- 

 table life, not even when detected in the very roots, which 

 support the whole structure, and are, it may be said, always 

 in the immediate contact of siliceous mixtures. Though clay 

 is comparatively a very soluble and tractable substance, and 

 possesses every capacity for combination with native acids, 

 yet this has never been included as one of the immediate 

 materials of vegetable organization. Thus, among other 

 instances, in the analysis of the roots of two polypodii, vul- 

 gare and filix mas, there were found silex, !ime, and mu- 

 riate of potash, but no clay. Moreover, it is known that 

 clay attracts carbonic acid from the atmosphere, which pro- 

 cess is supposed to be promoted by suffering lands to remain 

 faliow, and the clay becomes then more soluble; but this 

 cannot take place with silex, there is no such chance for 



• /Ijin. ce Chimie, torne xx\i. f IMd. tome Iv. 



rendering 



