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THE AMERICAN MUSEUM JOURNAL 



just as deep. Dense foliage of oak, 

 beech, sycamore, hickory, walnut, chest- 

 nut, dogwood, and other deciduous 

 trees, screens all but the most pro- 

 nounced scars on the sharper curves, 

 and whether you are on the river or at 

 the top of the gorge, you are seldom 

 permitted to see more of the landscape 

 than you can appreciate at a glance. 

 In the early morning hours of ^May 

 these woods were alive with song birds 

 and I was told, confidentially, that fisli- 

 ing was excellent in the stream; but 

 my own especial interest took me to 

 quite another world, the region whence 

 come the waters of the Green River. 



If one goes prowling over the for- 

 ested tal)leland, he soon becomes aware 

 of several unusual things. In the first 

 place, he cannot fail to notice occa- 

 sional eminences, sometimes of a py- 

 ramidal character and often several 

 hundred feet high. These heights are 

 known as "knobs," and they appear to 

 register for us the amount of erosion 

 to which this section of the country has 

 been subjected since it was lifted out 

 of the sea. Excellent as ''lookouts,*' 

 these knobs are, besides, of especial 

 interest to the archaeologist, because 

 many of them are also natural strong- 

 holds and as such were once occupied 

 by the Indian. In the second place, 

 the adventurer will be struck by the 

 singular fact that he finds no streams 

 to cross. Here and there he may dis- 

 cover valley-like depressions — some of 

 them large enough to swallow up an 

 appreciable slice of ]\Ianhattan Island; 

 but whether or not they have an outlet 

 to the river gorge, there is seldom any 

 water to be seen in them. Passing on, 

 he will encounter again and again sud- 

 den depressions of smaller dimensions, 

 some oval, some bowl-shaped ; some 

 perhaps less than fifty feet in depth 

 and diameter, and others possibly three 



hundred feet deep and several hundred 

 yards across. In a few instances a 

 small pool of water may reflect the slcy 

 and surrounding landscape, but ordi- 

 narily the big bowl is dry, and there 

 may be a visible hole in the bottom. 

 The really inquisitive explorer may dis- 

 cover a strong air current going in or 

 out of this hole; and if he sit down to 

 reflect at all on the strange phenom- 

 enon, a long series of observed facts 

 will soon fall into definite relations, 

 and the mystery of the Green Eiver 

 sources will be solved. In brief, the 

 whole three-hundred-foot limestone 

 formation between tlie top of the pla- 

 teau and the river level is actually 

 honeycombed with caverns; the depres- 

 sions in the plateau surface, known as 

 sink holes, are merely collapsed cave 

 roofs; and the rainfall on the plateau 

 is caught up in these thousands of 

 sink holes, which act as so many fun- 

 nels for the labyrinthian cave system 

 l)elow, that finally conducts it to the 

 river. 



How the water got started on its un- 

 derground course we cannot stop to 

 explain; but it has been at work prob- 

 ably for millions of years and has 

 literally eaten out several successive 

 systems of passages, the topmost vaults 

 being of course exceedingly old and 

 now in process of refilling. In the 

 Mammoth Cave, for example, there are 

 no fewer than five superposed sets of 

 galleries, the upper one being close to 

 the surface of the plateau and the lower 

 one so far down that the river floods 

 back up into it every spring. And the 

 Mammoth Cave is not a mere local 

 feature. There are said to be more than 

 eight thousand square miles of lime- 

 stone formation in Kentucky suitably 

 disposed for the development of im- 

 mense caves. This means that the state 

 possesses thousands of miles of subter- 



