EXEKCJSES. 449 



These caverns are also remarkable for the stalactites 

 and stalagmites they contain. The explanation of these 

 phenomena is as follows: The water, flowing through 

 limestone rocks, dissolves a portion of the lime, and on 

 reaching an opening, such as a cavern, at its sides or roof, 

 it forms a drop, the moisture of which evaporates, and leaves 

 a small circular plate of calcareous matter, which is increased 

 by the constant dropping of the water. In process of time 

 continual accumulations of this nature form long pendent 

 points like icicles ; for a stalactite may be said to be an icicle 

 of stone, as an icicle may be said to be a stalactite of frozen 

 water. When the supply of water holding lime in solution 

 is too rapid to allow of its evaporation at the bottom, of the 

 stalactite, it drops to the floor of the cavern, dries up, 

 and forms in like manner a stalactite rising from the ground, 

 which, for the sake of distinction, is termed a stalagmite, 

 Where the two unite, they form natural columns. The 

 most celebrated caves of this kind are the Grotto of 

 Antiparos, in 'Greece ; that of Adelsberg, in Styria ; and 

 AVeyer's cave, in the TJnited States. 



EXEECISES 



ON THE CABBONIFEBOTJS OB MOUNTAIN LIMESTONE. 



1. State the characteristics of the formation. 



2. Point out its geographical distribution. 



3. Trace its course on the map. 



4. Name the localities in which it prevails. 



5. Describe its organic remains. 



6. Mention its mineral contents. 



7. State any facts of general interest, and pursue the 

 method of question and reply as before. 



G G 



