LIMESTONES OF WESTERN TENNESSEE 569 



tion. The change from the solid limestone to the reddish clayey 

 rock takes place in different sections at different levels, so that 

 it is evident that parts included in the Dixon bed in one section 

 may be represented by hard limestone in another section, and 

 may there be included in the Lego bed. The Lego and Dixon 

 beds may therefore be regarded as one horizon, bounded by the 

 Waldron bed below, and the Brownsport bed above, changing 

 from a series of limestones beneath to a series of clayey rocks, 

 usually red in the Tennessee River basin, above. 



6. West of the Teimessee River. — Both the Lego bed and the 

 Dixon bed are exposed at many points between Swallow Bluff 

 and Perryville. At Swallow Bluff the lower part of the Lego 

 bed, 28 feet thick, is exposed along the river, below the landing. 

 At Bath Spring the top of the Dixon bed is 67 feet above the 

 level of the spring. West of New Era the Dixon bed is well 

 exposed along the road from Vice's store to Brownsport Furnace. 

 At the furnace, south of the store, Orthoceras amycus occurs i 5 

 feet below the top of the Dixon bed. The Dixon bed is well 

 exposed at the base of the mound glade, a quarter of a mile 

 north of the home of Noah Butler, 2)4, miles north of Vice. 

 Exposures of both the Dixon clay and the Lego limestone are 

 common within 2 miles of DixonSpring. The Dixon bed usually 

 forms the lower part of the glades so frequent in this part of 

 Tennessee. No attempt has been made to determine the thick- 

 ness of these beds on the western side of the Tennessee River. 



According to Professor Safford, the reddish limestone below 

 the Dixon bed is quarried on Birdsong Creek in Benton county, 

 and in the southern part of Henry county, on the Big Sandy 

 River, where a local but a wide dome brings this bed to the sur- 

 face. 



III. BROWNSPORT BED. 



7. Eastern line of outcrop. — The most eastern exposure of the 

 Brownsport bed is at the bridge, i y^ miles west of Pegram, and 

 about 21 miles east of Dickson. Here the base of the Browns- 

 port bed, consisting of clay, 8 feet thick, is directly overlaid by 

 the Mesodevonic limestone, most nearly related to the Onondaga 

 or Corniferous. At Montgomery mill, the top of the Silurian 



