34 GEOLOGICAL RECONNOISSANCE 



elm, pecan, black walnut, sweet-gum, hackberry, and buckeye, with an 

 undergrowth of very large papaw, cane, grape vines, and a little spice- 

 wood. 



Rye flourishes well on this soil; but it is too rich for cotton, which grows 

 too rank and runs too much to stalk and leaf. Timothy succeeds well; 

 clover has not been tried. It is, however, especially adapted for small 

 grain, for which, indeed, it is celebrated. The explanation of this will, 

 no doubt, be found in a geological cause which will hereafter be adverted 

 to. Since the wheat does not freeze out of this soil, and the weevil is 

 unknown in the country, the farmers are most favorably situated for rais- 

 ing this grain, and the natural resources of the country would justify the 

 erection of extensive flouring mills. 



The water obtained by digging wells in the Oil-trough bottom is quite 



soft. 



The Oil-trough bottom is about 15 miles long. At its head, the first 

 ridge encountered is known as the Oil-trough ridge. Here 1 found the 

 first ledges of solid rock Avhich I had seen since leaving Greene county. 

 These proved to belong to the upper members of the subcarboniferous 

 limestone formation. At 70 feet above the Oil-trough bottom, I found 

 one of the members of this formation which marks most decisively a most 

 impartant geological horizon, viz: the Archimedes limestone. This rock 

 occupies a position below the lowest workable coal throughout the western 

 states of North America. No exception has yet been found to this geolo- 

 gical axiom; it, therefore, serves as a sure and safe guide in pronouncing 

 as to the existence or non-existence of coal in the vicinity, and furnishes 

 the clue to the geologist, in connection with the dip and strike, of the for- 

 mations of the country, in what direction he must search for coal. 



The total height of the Oil-trough ridge was found to be 152 feet, and 

 the following members of the upper subcarboniferous group of rocks 

 were observed at the different elevations herewith subjoined in the 

 approximate section of that ridge: 

 At 152 feet, Sandstone. 

 " 1 15 " Third bench of protruding limestone; exposed for 15 feet. 

 " 115 " Limestone shale. 



" 92 " Second bench of protruding limestone; exposed for 15 feet. 

 " 75 " Productal black limestone. 

 " 70 " Archimedes limestone. 



" 56 " First projecting ledge of limestone seen in this part of the 

 ridge. 

 The Archimedes limestone, as above remarked, is the index to the dis- 

 covery of coal. Where the sub-carboniferous limestone is fully developed 



