204 THE MAMMOTH CAVE. 



formation. We will explain the process in the 

 language of Dr. Wright, which we do not think 

 can be improved upon either in point of fact or 

 brevity : 



"When water, holding the bicarbonate of 

 lime in solution, drops slowly from the ceiling, 

 by which it is exposed to the air sufficiently 

 long to allow the escape of one equivalent of car- 

 bonic acid gas, the lime is deposited in the form 

 of the proto-carbonate of lime. If the deposit 

 occurs in such a manner that the accumulation 

 takes place from above downward, in the form 

 of an icicle, it constitutes what is termed a sfa- 

 lactite; but if it accumulates from below up- 

 ward, it is called a stalagmite. Stalactites and 

 stalagmites frequently meet in the center and 

 become cemented, by which a column of support 

 is formed." 



If the limestone which forms the stalactite is 

 perfectly pure, it will be white, or semi-transpa- 

 rent; if it contains oxide of iron, it will be of a 

 red or yellowish color. The black stalactites 

 contain a large proportion of the black oxide of 

 iron. 



Leaving Gothic Chapel, and pursuing our 

 course, we are next introduced to Vulcan's 

 Smithy, a room the floor of which is strewn* 



