116 PHYSIOGRAPHY, 



Carbonic-Acid. 



2. Analysis. 



By BJERZELIUS. 

 Carbon 27-40 



Oxygen 72-60 



3. It is found in the largest quantity and highest degree of purity upor 

 the surface of carbonated springs, and in caves; in which cases it issue; 

 directly from the earth. Of the most remarkable of these sources of the 

 present species in the United States, are the springs of Saratoga anc 

 Ballstown near Albany. An ingenious hypothesis to account for the or- 

 igin of the carbonic acid in these localities, and many others of less im- 

 portance in the vicinity, has been proposed by Prof. EATOK. The rock 

 through which the waters rise is an argillite, containing large quantities 

 of iron-pyrites and carbonate of lime. The iron-pyrites, he conceives, i< 

 decomposed by water, the sulphuric acid thus formed being in contact 

 with the carbonate of lime, gypsum is produced, and carbonic acid dis- 

 engaged ; which being situated at great depths in the earth, and conse- 

 quently under great pressure, combines with water in large proportions; 

 and when the waters thus charged issue from the earth, the pressure be- 

 ing removed, they part with their superabundant carbonic acid. The 

 well known mineral springs of Tunbridge and Carlsbad are remarkable 

 for the evolution of this acid gas. It issues from a small cave in the side 

 of a mountain near Naples, the floor of which, to the depth of a foot or 

 more, is covered with a stratum of this noxious fluid, into which, if a 

 dog be introduced, he is immediately suffocated. It has hence been 

 called the grotto del cane. Another cave of a similar character exists 

 in the Bttdb's hegy, a porphyry mountain in Transylvania. Carbonic 

 acid is also emitted from certain marshes, and from the solfataras. In ad- 

 dition to the foregoing sources of this species, it is formed abundantly by 

 the combustion of all substances that contain carbon, the respiration of 

 animals, and the spontaneous changes to which dead animal and vegeta- 

 ble matter is subject. Accordingly, it is always present in the atmos- 

 phere, even at the highest elevations. All kinds of spring and well- 

 water contain it dissolved in them, and to the presence of which they are 

 partly indebted for their agreeable flavor. Where carbonic acid is evol- 

 ved in low situations, it is liable from its gravity to accumulate ; a cir- 

 cumstance which often happens in deep mines and wells, in which it 

 forms an atmosphere known in English by the name of choke-damp, in 

 German by the name of Schwaden or Swath. 



