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 s/a-_ 
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 
