DOMAIN VI. CARBONACEOUS. 541 



the most ancient of all the rocks. Char- 

 coal is now regarded as a mixture of car- 

 bon and hydrogen. By combustion it is carbonic acid, 

 converted into carbonic acid gas, formerly 

 called fixed air, or aerial acid; whence 

 some writers have used the epithet aerated 

 lime, barytes, &c. for what are now called 

 carbonates of lime, barytes, and the like. 

 The discovery of this new air by Dr. Black, 

 led to wonderful improvements and a total 

 renovation of chemistry, which in its pre- 

 sent form has been called pneumatic, from* 

 its spiritual foundations. It is indeed re- 

 markable, that the profoundest study, and 

 the most patient experiments, should con- 

 duct us from matter to spirit ; and thence 

 by a natural gradation of thought, to that 

 ineffable spirit, the Creator of the uni- 

 verse. 



The carbonic acid gas, more briefly call- 

 ed carbonic acid, forms a constituent part 

 of the atmosphere, in the proportion of 

 about 1, in the ]00, while the remainder 

 consists of about 77 of nitrogen and 22 of 

 oxygen gas. Combined with the earths, it 



