358 O^"" '^HE ANTIQUITY OF THE CAVERNS 



mile ; each is the entrance to a cavern channel, and 1))' their numbers they enable lis to 

 estimate the extent of the ramifications of the caves beneath. There is no douljt that the 

 atro-reo-ate length of the channels accessible to water is many tens of thousands of miles in 

 Kentucky. I am inclined to think that the truth would not be overstated if we say that 

 there are at least one thousand miles of open water channel beneath the surf;ice of the car- 

 boniferous limestone belt in Kentucky. Owing to the rapid rate of the down cutting of 

 these channels, and the massive nature of their walls, they remain open for a surprising 

 length of time, and are so deep that they are rarely swept clean Ijy the floods of the rainy 

 season. Generally there are several levels to these channels, the upper of which have 

 Ion"- since been abandoned bv the water. These streams gather themselves together as 

 above ground, and the channels soon become excavated into broad wa^-s or caverns access- 

 ible to animals of any size, provided an opening is broken to the surface. Although this 

 limestone is singularly massive and homogeneous, it yet varies somewhat in its various beds. 

 A more resisting bed holds the streams in one level for a long time, and this makes a tier 

 or floor of caverns. When the resisting bed is penetrated, as it generally is, by some stream 

 passing from above, the water begins to excavate another floor, and that aljove is aban- 

 doned to the forces which tend to close it. When much water oozes into these stream-de- 

 serted caves, bringing with it matei'ials to form stalactitic masses, we have forces which tend 

 to close the cave, and often accomplish that work. Tliere are channels in the Mammoth 

 Cave which are far gone to destruction by this process, and some which have doubtless been 

 entirely destro^^ed by this action. Most usuall3\ however, the process of excavation goes 

 on widening the cavern until the roof fails to sustain the weight, and we have great fixlls of 

 stone tending to block the road of the stream and compel it to work another way. After 

 being abandoned we sometimes find these caverns lasting for an extremely long time without 

 change. The upper levels of the Mammoth Cave have doubtless remained substantially 

 unchanged for hundreds of thousands of years. Stalactitic matter is kept from forming by 

 the impervious roof, and by the small amount of limestone between the top of the cavern 

 and the soil, which does not admit of the water becoming very much charged with lime in 

 its passage to this level. 



As the streams gather force they begin to use moving pebbles as teeth for their cutting 

 work, and thus pass more rapidly froui stage to stage. It may be in part to this that we 

 owe the fact that the lower chambers in the series are quite generally smaller than the 

 up[)er chambers. Most of the grand avenues known to me are on the upper level of the 

 cavern work. 



The most surprising features in the architecture of caverns are the great " domes " or 

 wells which often pass at one leap from the uppermost to the lowermost level of the caves. 

 These are uniformly caused l)y streams, which by one cause or another secure in the begin- 

 ino-, while they flowed on the upper level, a vertical descent of greater or less height. 

 Often it is a " sink hole " from the open air, which begins the vertical channel. As soon 

 as a beginning is made, each additional foot of depth adds to the force of the torrent. The 

 sandstone above and the flint beds of the limestone itself, fiu-nish a plentifid supply of 

 pebbles to give energy to the cutting action. Thus we see these caverns in their fullest 

 development consist of the following elements : the tubes leading from the sink hole or 

 funnels of the surftice to the gathering bed or uppermost set of caverns ; then a succession 

 of levels of caves connected by vertical shafts formed as before described, or by breaks in 



