87 



its mineral waters, now rendered famous by extensive exploitation, from 

 the uplands of the Mitchell limestone, some fifteen or twenty miles to 

 the eastward. These waters, which reach the deeper zones of flow, are 

 always strongly impregnated with mineral salts. Much of the mineral 

 water of the French Lick Valley comes from a depth of 400 to 500 feet. 

 Owing to the depth to which it descends and distance which it travels, 

 the w'ater has been brought into intimate contact through a consider- 

 able interval of time with these eminently soluble limestones and its 

 highly mineralized condition is an evidence of the vast amount of ma- 

 terial removed from them, most of which, however, has undoubtedly been 

 derived from a comparatively superficial zone. 



The most conspicuous effects of solution are those produced at or 

 near the surface of the rock, and it is these that the photographs pre- 

 sented herewith illustrate. In quarry openings where the rock has 

 been taken down along a joint plane, so as to expose the wall of one 

 of these avenues of ground-water, the effects of solution are shown in 

 greatest perfection of detail. The dip .joints are often greatly enlarged, 

 their walls pitied and honeycombed, and traversed by arborescent sys- 

 tems of small openings through which the carbonated waters have eaten 

 their way; and the once solid rock is reduced to a crumbling earthy sub- 

 stance stained and rusted with iron. Where two joints (dip and- strike) 

 intersect, the enlargement is apt to be greatest, giving origin to funnels, 

 narrowing gradually downward, and showing in a beautiful way the 

 method of formation of sinkholes, which are only such funnels of solu- 

 tion grown large." 



Where the surface of the limestone has been denuded of soil, for 

 quarrying purposes, it is found to be corroded to a remarkable extent. 

 Every dip joint now becomes a ragged furrow, and between joints the 

 rock rises in hummocky ridges, the hog-backs of quarryrnen. Toints and 

 knobs and mushroom-like projections meet the eye at every turn — be- 

 wildering in variety and impossible to describe. The hog-backs frequently 

 stand as high as a man's head, and their flanks are scarred and scored by 

 the all pervasive attack of the dissolving water. 



Except where the activities of man or nature have removed it, a 

 blanket of red soil overlies and hides this marvelous complex of cor- 

 roded rock. The red soil or clay is the minute remnant of the original 

 rock, left after the lime carbonate has been carried away in solution by 

 the water. It is the insoluble residue. So complete has been the removal 



