O", 



76 0?i the Identity of Silex and Oxygen, 



a portion, from their surfaces, to the surrounding Hiedwim 

 in which they are imbedded. 



The degradation of these flint-stonea is, likewise, strongly 

 marked by a peculiar opacity, not unlike white glass-enamel 

 or the superior kinds of porcelain ; and this forms a well- 

 defined stratum, which covers entirely the whole surface of 

 the stone, penetrating it to a greater or Tcss depth. It cannot 

 be considered as a very forced explanation, to aay, that this, 

 may, probably, be the very point of contact, where this de- 

 clension of sHex is the commencement of a new modifica- 

 tion ; and that this terminates eventually in the perfection of 

 a carbonate, or even of the lime itself, of which silex would 

 their be considered as the independent progenitor. 



That the blunted and nodular shape of the generality of 

 siliceous stones, is a mark of loss in the primitive mass it- 

 self, may be explained by many examples. Thus, even ia 

 common experiments, a sharp or crystal -formed piece of 

 any substance, capable of solution in an acid, soon loses it* 

 projecting corners, and, as the action of the acid proceeds,, 

 gradually becomes less indented, and more smooth or globu- 

 lar. It is rather a gratuitous conclusion, when the convex 

 .«hape of pebbles, gravel, and all othet siliceous- stones, is 

 ascribed to attrition : in some instances this argument may 

 appear just, but in the more hnportant cases it is, I con- 

 ceive, extremely fallacious. 



The true nature of clay, or, as it is now generally called, 

 alumincj. vvh«n eonsidered as a primitive earth and simple 

 element, seems very questionable ; for, notwithstanding 

 various met^hods have been employed to obtain it ma state of 

 purity, still this doubt remains. Even, in one of the most 

 celebrated systems of chemistry, after detailing the best 

 BBode to accomplish the end, the ^author adds, that the 

 »lumine ^ will then be nearly pure." One of the specific 

 characters, peculiar to clay, tends very much to confirm 

 this suspicion ; it is that particular odour, constantly evoI«* 

 ving from it, ])erceptible on all occasions, such as ploughing 

 or stirring upland or garden-groimd, and which is familiarly 

 known by. the term earthy smelL 



It 



