HOT SPRINGS, ARKANSAS. 85 



IGNEOUS ROCKS. 



Besides the sedimentary rocks just noted there are four narrow dikes 

 of igneous rock about one-half mile south of the mountain borders and 

 near the city limits. These rocks are dark-colored mica traps, a form 

 of rock called "ouchatite." They are chiefly interesting because they 

 show that there was some deep-seated body of molten material from 

 which the dike fissures were supplied. Small dikes are found north 

 of the city, east of the city, and in considerable abundance about Pot- 

 ash Sulphur Springs and at Magnet Cove. These dikes have a gener- 

 ally ESE.-WNW. direction, showing that the fissures are parallel 

 to the mountain sides. They are from 1 to 4 feet wide and are gener- 

 ally much altered, so that the outcrop is inconspicuous, or is covered 

 by vegetation, and when the rock is broken black mica in small flakes 

 is the only mineral seen. 



FOSSILS. 



The age of the sedimentary rocks is determined by the fossil remains 

 found in them. The black .shales which underlie the novaculites 

 contain remains of a curious hydrozoa. These fossil remains are known 

 as graptoUtes, and the forms identified at the Hot Springs belong to the 

 upper part of the Lower Silurian age (Trenton and Utica). New 

 types of these fossils peculiar to the Hot Springs are illustrated in 

 the Novaculite report issued by the Arkansas geological survey. 

 Besides these curious forms, a few shell remains Qyrachiopods and 

 larnelUbraneTis), corals, and worm trails have been found. The grap- 

 tolites occur on the north side of the hill on a small stream drainage 

 on the west side of the continuation of Park avenue. They are also 

 seen in a very black shale forming the bluff on the west side of Park 

 avenue above the Hotel Hay and below the Barnes House. Similar 

 fossils also occur on Whitington avenue, one-fourth of a mile above 

 the head of Central avenue, at a point where the creek crosses the 

 street. 



Plant remains of Lower Carboniferous age have been found in the 

 shales exposed in the excavation for a cellar on the western side of 

 Malvern avenue, 100 feet north of the Park Hotel. The shales are 

 varicolored, brown, red, gray, and black, but the fossils occur in the 

 olive-colored, sandy shales. Similar fossils were also found in Ouach- 

 ita avenue at the Hot Springs. 



OCCURRENCE OF THE HOT SPRINGS. 



The hot waters issue from the base and lower portion of the slopes 

 east of the valley. This area is a narrow strip, a few hundred feet 

 wide, and a quarter of a mile long. In its general aspect this area is dis- 

 tinguished from the rest of the mountain by its patches of barren gray 

 tufa, the old hot-spring deposit, and the absence of forest growth. From 

 the descriptions given by earlier writers, it is evident that this difference 

 in appearance and vegetation was formerty very marked. To-day the 

 springs are all covered, and mostly concealed beneath turf and shrub- 

 bery. The old tufa deposit is in large part covered by soil and plants. 

 The creek is arched over and sidewalks and roadways are built on it. 

 The space between creek and hillside is covered by the bathing establish- 

 ments, which, in many instances, are built directly over large springs. 



