It contains extensive beds of a yellowish white siliceous stone, which is often somewhat translucent, and resembles some varieties of hornstone. Its fracture is a little splintery, and sometimes largely conchoidal; it is of a close texture, but the recent surface is generally destitute of lustre. It is this rock which affords the stones called Washita oilstones. It may, with propriety, be denominated petrosilex. This name is, however, to be understood as having the application given it by Kirwan,[34] who uses it to designate the fusible varieties of the hornstone of {150} Werner, and not the several varieties of compact felspar to which it has been sometimes applied. In passing from the hot springs, north-east to the lead-mine country, about the sources of the Merimeg, this rock is found to be intimately connected, and to pass by minute and imperceptible gradations, into the flint rock of that district, which is decidedly secondary, and of contemporaneous origin with the compact limestone which it accompanies. About the hot springs it is not distinctly stratified, but occurs in very extensive masses, sometimes forming the body of large hills, and is marked by perpendicular seams and fissures, often placed very near each other. The hot springs of the Washita are in north latitude 34° 31´, and west longitude 92° 50´ 45˝,[35] near the base of the south-eastern slope of the Ozark mountains, and six miles north of the Washita. They have been erroneously represented as the principal sources of that river, which are more than one hundred miles distant.[36] We have been informed that these remarkable springs were unknown, even to the American hunters, until the year 1779. At that time, it is said, there was but one spring discharging heated water. This is described as a circular orifice, about six inches in diameter, pouring out a stream of water of the same size, from the side of a perpendicular cliff, about eight feet from its base. This cliff was situate then, as it is now, along the eastern side of a small creek, but was at a greater distance from the stream than at present. At another place, near the top of the mountain, which rises abruptly towards the east, the heated water is said to have made its appearance near the surface of the ground, in a state of ebullition, and to have sunk and disappeared again upon the same spot. It is probable these representations {151} are in a great measure fabulous; all we are to understand by them is, that the gradual augmentation of the thermal rocks, which are constantly forming about the springs, has changed the position, and perhaps increased the number of the orifices.[37]