258 ON A NATUR \L SYSTEM 



If the later dcpofitions diflcr in their colour and 

 properties from thofe of an earlier date, yet the. 

 original organic llruclure is beautifully difplayed 

 by fmooth and polilhed fcdlions of the diifercnt 

 bodies. All the particles, however, of the bo- 

 dies fo dellroyed are not always carried off; for 

 it often happens in dill illation, that fuch are ex- 

 pelled as fhcw iigns of an organic con A rail ion, 



J en. Organic Bodies penetrated with metairu 

 Panicles. 



TJIE moft fubtle'mctallic molecules, that can 

 poffibly be canicd along by water, may in the 

 fame manner penetrate and change the harder 

 organic parts. 



cm. Nuclei. 



FROM the fubilances already defcribed, nu- 

 clei have, with great propriety, been confider- 

 ed as quite dillinct. They are produced by two 

 diiferent proceilcs. Any body pollening a ihell 

 or firmer covering, and depoiitcd in a loft ftra- 

 tum, is gradually attacked in its llefhy parts 

 and foft inteilincs, \\ hich are either wholly de- 

 llroyed, or contracted by exficcation ; fo that 

 room being made in this manner tor the parti- 

 cles flowing in, the (hell is at length filled with 

 a nucleus, bearing the marks of its internal fur- 

 iacc. If a body is involved in iediment, and 

 after the exliccation of the (Iratum is any way 



dellroyed 



