au ON A NATURAL SYSTEM 



power of attraction, form at once the growtfy 

 and perfection of foflils, 



xvin. Variable and incanjlant Form of Foffik. 



FORM, and other external qualities, of which 

 the fenfes only can determine, depend upon 

 circumilanccs that are perpetually varying, hut 

 which do not in the leall a fleet the intrinfic na- 

 ture of the fofiil. 



The poll Lion may poflibly need the illuftra- 

 tion of an example. Let us take a quantity of 

 water, charged with aerated calcareous parti- 

 cles, and we fliall fee arifc various figures, tex- 

 tures, and cofiefions, according to the different 

 modes in which the concretion was performed. 

 By the fubfidcnce only of the atoms a crufl is 

 generated, parallel to the bottom, if the dillrt- 

 Lution of them has been made equally through- 

 out the whole mafs; if otherwifc, the greater 

 part forms tubercles farther from the furface of 

 the bottom, than in the fuppofhion of equality. 

 Water impregnated with aerial acid actb like a 

 nicnftruum ; and, though it does not at all aifcct 

 the faturated particles in this hypothecs, yet it 

 neverthclefs has conilderuble inilucnce in form- 

 ing their concretions. Such water oozing 

 through fubtcrrancous vaults, generates calca- 

 reous drops, hanging from the rcof, wliile 



x pointed 



