378 DOMAIN V. CALCAREOUS. 



bination ; while that of the ancients is often 

 -a stalagmite, or secretion of common lime- 

 stone. With fluoric acid, calcareous earth 

 becomes fluor, or fluate of lime. 



The greater proportion of limestone is 

 produced by the decomposition of marine 

 shells ; but the more ancient, which is crys- 

 tallised, and presents no trace of such re- 

 mains, is called primitive, being supposed 

 as ancient as any of the rocks. It is in 

 general easily distinguished from the other 

 substances by the nitrous acid, formerly 

 called aqua-fortis, which excites efferve- 

 scence; but when mixed with magnesia, or 

 much silex, this effect is slowly procured. 

 Nor do gypsum nor fluor effervesce. 



To these observations, which are chiefly 

 extracted from Kirwan, Thomson, and Pa- 

 trin, it may be added that, in 1808, Mr. 

 Davy reduced lime to a metal, which had 

 the colour and lustre of silver, and burnt 

 with an intense white light into quick lime. 



In some works of mineralogy the first 

 three Modes of this Domain, and even the 

 three succeeding, have been arranged as 



