280 GEOLOGY OF ILLINOIS. 



and sub-crystaliue limestones, intersected with vertical fissures or joints, 

 probably resulting from the shrinkage of the material on crystalizntion. 

 The beds vary in thickness from one to six feet or more, and contain a 

 few of the characteristic fossils of this horizon, among- which lieecptii- 

 culites Oicenan-a, Orthia lynx, 0. testudinaria, 0. formosns and Rliyncho- 

 nella capax were obtained at this point. 



Along the western face of this limestone escarpment, where it attains 

 its greatest elevation, tall columns of limestone, locally known as the 

 " Stone Chimneys," stand out entirely isolated from the face of the bluff, 

 from which they are now separated by a space of from ten to twenty 

 feet or more in width, the intervening portions of the limestone having 

 been removed by surface erosion. Originally these columns were proba- 

 bly only separated from the adjacent cliff by one of the narrow fissures 

 already mentioned as common in this limestone ; but these have gradu- 

 ally widened, by the long continued action of atmospheric influences, 

 until they are now many feet away from the rock to which they were 

 originally united. These columns, seen from below, when the leaves 

 have fallen from the dense forest in which they stand, present a very 

 grand and picturesque view, and resemble the ruins of some ancient 

 castle. Some of them are from forty to fifty feet or more in hight, and 

 others have toppled down, and the huge blocks of limestone of which 

 they were composed now lie scattered along the base of the cliff. There 

 is but one other point in Southern Illinois where this limestone appears 

 above the surface, which is at the " Grand Chain," just below Thebes, 

 in Alexander county, where it forms the nucleus of another anticlinal 

 axis crossing the river at that point. It appears to be stratigniphieally 

 equivalent to the " Galena Limestone," the true lead-bearing rock of 

 the Northwest; but we saw no evidences of its being a mineral-bearing 

 rock in this portion of the State, nor does it possess the dolomitic char- 

 acter which prevails in its north-western outcrops. 



This limestone furnishes the celebrated " Glencoe marble," of Glen- 

 coe, in Missouri, and inexhaustible supplies of the same marble, equally 

 as good as that from the locality above cited, might be obtained from 

 the Trenton limestone at Salt Lick Point. A railroad from St. Louis 

 to Chester, down the American Bottom, would render this rock at once 

 available, as well as various other quarries of excellent building stone, 

 that could be opened in every township through which the road would 

 run in this county. The time is not far distant when the demand for 

 such materials will justify the building of a railroad along the foot of 

 the Mississippi bluffs between the points above named. 



