FORMATION OF THE CAVE. 



to correct a popular error concerning the formation of the beauti- 

 ful structures that adorn the ceilings of some portions of the cave. 

 In the dryer localities, where the floors are dusty and everything 

 indicates the prolonged absence of moisture, the ceiling is covered 

 with a white efflorescence that displays itself in all manner of 

 beautiful shapes. It requires no stretch of the imagination to dis- 

 cover among these, the perfect forms of many flowers. The lily 

 form prevails, and the ceilings of many of the chambers are cov- 

 ered with this beautiful stucco work, surpassing in delicacy and 

 purity the most beautiful workmanship of man. These are not 

 produced, as many suppose, by the dripping of water, and the 

 gradual deposit of sulphate of lime upon the outer portions. The 

 stalactite is formed in this manner, but these are neither stalacti- 

 form, nor are they produced in a similar way. Dripping water 

 is the agency that forms the stalactite, while the efflorescence 

 in the dryer portions of the cave cannot take place where there is 

 much moisture. The growth of these beautiful forms is from 

 within, and the outer extremities are produced first. They are 

 the result of a sweating process in the limestone that forces the 

 delicate filaments of which they are composed through the pores 

 upon the surface of the rock, their beautiful curved forms result- 

 ing from unequal pressure at the base, or friction in the apertures 

 through which they are forced. Mr. L. S. Burbank, of Lowell, 

 Mass., has kindly furnished us with the following abstract of his 

 opinions upon this interesting subject. 



' The rosettes, wreaths, and other curved fibrous forms of gyp- 

 sum, in the Mammoth Cave, occur only in particular strata of the 

 limestone which do not appear in the first part of the long route. 



Their formation may be explained in this way : that portion of 

 the rock where they are found consists of carbonate of lime, with 

 some impurities, and contained originally the sulphide of iron, or 

 iron pyrites, disseminated in small grains or crystals, and also in 

 rounded nodules or concretions, sometimes of considerable size. 



By exposure to air and moisture, oxygen unites with both the 

 sulphur and the iron, producing sulphuric acid and oxide of iron, 

 which combined, form a sulphate of iron. Then a double de- 

 composition takes place ; the sulphuric acid unites with the lime 

 to form the gypsum ; the carbonic acid of the limestone combines 

 with the oxide of iron, forming a carbonate of iron, and this, on 

 further exposure, parts with the carbonic acid, and leaves the 

 brown coating of oxide, which is seen in many places on the sur- 

 face of the rock. 



The gypsum is thus constantly forming in the rock, and, being 

 soluble, is carried by the water to the exposed surface where it 

 crystallizes. 



The crystals appear to grow out from the rock by additions from 

 beneath, which continue to push the ends first formed, and if these 

 do not become attached to other parts of the rock, straight needle- 



