Limestone Caves. 
235 
( 4.) Carbon dioxide is given off abundantly in volcanic 
regions. 
There is, therefore, no lack of carbon dioxide, and 
hence it is that most natural waters contain carbonic 
acid. All rivers and springs, therefore, that pass 
through or over limestone rocks, contain carbonate of 
lime in solution. 
“ The most clear and sparkling waters often 
contain a quantity of dissolved limestone, just as the 
sea contains a quantity of dissolved salts and other 
matters, and both may be made, by evaporation, to 
deposit their contents in a solid form. Water trick- 
ling through the roofs of limestone caverns, and 
partially evaporated as it falls, deposits the pre- 
viously dissolved limestone it contained in the form of 
stalactites and stalagmites ; and brooks and rivers, 
when broken into spray, in like manner deposit masses 
of limestone called Travertine or Tiburstone. Encrus- 
tations are made in this way, both naturally and 
artificially, and the substance deposited is precisely the 
same as that of statuary marble, and is often just as 
crystalline, and will take as high a polish.” 1 
With regard to stalactites, which so quickly arrest 
attention in limestone caves, Dr. Manteil, in his 
Wonders of Geology , graphically describes the origin 
and the picturesque appearance of these singular 
masses of rock : — “ One of the most common appear- 
ances in limestone caverns is the formation of 
1 Jukes. ‘‘School Manual of Gfeology,” p. C9. 
