Camping and woodcraft - Scoutmastercg.com

CAVE EXPLORATION 343ried below, which, being whirled about in a vortex,rapidly cut the walls of the cave bed. Nodules offlint, washed out from the honeycombed rock above,lend powerful aid to this grinding and drillingprocess. Thus in time a large chamber is excavatedbelow the main fissure and an underground riverfinds its channel to some exit which may be milesaway.When a cave chamber forms near the surface ofthe ground its arch or vault may gradually weakenuntil it can no longer sustain the weight overhead.It collapses, leaving a pit strewn with rubbish thatSlowly some ofwas formerly the dome of the cave.this rubbish is pulverized and washed away. Theedge of the pit w^ears smooth and sloping sides areformed, tapering downward to a common center.The result finally is a funnel-shaped cavity in theearth that we call a sink-hole.Abysses.—In some districts, as in the cavernousregion of Kentucky, these sink-holes, varying greatlyia size, may average a hundred to the squaremile. Occasionally one will be found that coversseveral acres and descends gradually to a hundredfeet at its throat. The distance thence downwardthrough a pit or dome to the floor below is usuallynot great, but in some Instances exceeds a hundred,or even two hundred, feet. The Devil's Hole,near Fordland, Mo., is so deep that when largelogs are tumbled into it they are never heard tostrike bottom ; but I have not learned of any trustworthymeasuring having been done at this place.It is claimed that the famous Rowan Pit in Yorkshire,England, has been descended vertically sixhundred feet without finding" bottom. How truethis may be I do not know. Strange errors havebeen made by earnest and sincere men in ''measuring"pits and caverns. I will quote a remarkableexample from Mr. Hovey:'Tldon Hole ... Is a famous oit in the Peak ofDerbyshire, about which Hobbes wrote in hntln