( H6 )• 



proper to this flint. The change of colour is 

 accompanied by a difference in the hard- 

 nefs, which fucceflively increafes, as appears 

 from its fcintillation with fteel ; the white 

 part of the ftone yielding no fparks ; the 

 light red, very few ; but the deep red, or 

 black, aiFording them plentifully. If. a 

 flream of nitric acid be poured from one 

 end to the other of fuch a piece, where the 

 colour is white an, efferi'efcence arifes, 

 which becomes lefs fenfible in the pale red 

 parts, diip.inifhing as that colour increafes, 

 until no appearance of it is difcoverable 

 where the rednefs is deepeft, and the fcintil- 

 lation with fteel ftrpngeft. Thefe charac- 

 ters, however, to the chemical eye are not 

 decifive of the fadt in queftion. For, not 

 to mention that difference of colour never 

 conftitutes a diverfity of fpecies in either of 

 the three kingdoms of Nature, the proper- 

 ties of hardnefs, and giving fparks with 

 fteel, do not exclude the prelence of carbo- 

 nate of lime ; fmce, though it has been con- 

 fidered as the diftinguilhing property of 

 calcareous carbonates, that they do not af- 

 ford 



