HOT SPKINGS, AKKANSAS. 89 



ally breached in the development of a larger water supply from the 

 spring. (Plate V.) Above the music pavilion another area of tufa 

 indicates the former presence of springs at a level higher than any 

 now existing. 



The thickness of the tufa deposit is likely to be overestimated, as it 

 covers steep slopes and even cliff faces. 



The earliest description of the place tells of its forming overhanging 

 masses alongside the creek, whose flood waters swept away its sup- 

 port. The natural exposures of conglomerate and sandstone outcrop- 

 ping near the pavilion show that the tufa is there underlain by hard 

 rock. Farther west, however, the tufa overlies soft, shaly rocks, 

 which have been digested by the hot waters and vapors for so long a 

 time that the material is as soft as ashes, and in the development of 

 new water supplies near Spring No. 1 a pipe was driven 38 feet down 

 into this material. Immediately beneath the tufa there is a breccia of 

 novaculite sandstone or shale fragments cemented by iron oxide, man- 

 ganese oxide, and carbonate of lime. This is seen under the tufa at 

 the Cave spring and at the Dripping spring. It merely represents 

 the old hillside debris cemented by the hot-water deposit and material 

 deposited later beneath the tufa mantle. 



The owners of the Hale bath house have cut a short tunnel into the 

 tufa back of their establishment, and the natural heat of the ground is 

 used for a vapor bath. There is no doubt that the ground back of 

 Bath House Row is permeated by a network of fissures and is heated 

 by hot-water vapors. 



Vegetation of tufa area. — The tufa area is described by all earlier 

 writers as being distinguished from the adjacent slope by its peculiar 

 vegetation. In the improvement of the reservation this distinction 

 has been largely obliterated, as flowers and shrubs have been freely 

 planted. The tufa cliffs and rougher exposures show, however, the 

 limestone-loving ferns Cheilanthes alabamensis Kunze and Adiantmn 

 capillus-veneris L., which occur nowhere else in this region. Owen 

 mentions these ferns especially, besides numerous peculiar mosses and 

 alga?, and the stonecrop, sage, lobelia, and senna as characteristic of 

 the tufa area. 



GEOLOGICAL RELATIONS OF THE HOT SPRINGS. 



In the geological sketch already given the rocks from which the hot 

 waters issue are described as sandstones and shales of Lower Silurian 

 age, occurring in sharply compressed folds. The hot waters issue from 

 the sandstones seen well exposed back of the superintendent's office 

 and near the music pavilion, and from the overlying shales in the area 

 west of the pavilion. These rocks form part of a steeply dipping anti- 

 cline plunging beneath the surface toward the southwest. It may be 

 compared to the partly buried prow of an upturned boat. The rocks 

 arch around the mountain slopes, the different beds being revealed very 

 much as the scales of an onion bulb are exposed when it is partly cut 

 into. While the rocks are flexed into this great curve, the great and 

 thick beds of hard sandstone and conglomerate were cracked while 

 being flexed, and little slips and breaks occur. The smaller cracks 

 form a network of fractures, which in some places are seen to be filled 

 with white quartz. The map shows the principal springs to be arranged 

 along a line running about NNE., or parallel to the axis of the fold 



