81 



strata of the formation, and we do not see the white rock again 

 below Jordan's Ferry, (Plate VII) except in thin patches at 

 tops of some of the bluffs. The character of the material of 

 these lower beds may be seen from the analyses of specimens 

 taken from Jordans and Belmont and Roe's bluff, Nos. n, 12, 

 13, and 14. The two specimens from the last-named locality 

 represent the composition of the prevailing dark-colored! argil- 

 laceous rock and of the lighter-colored ledges. (Plate VIII.) 



At Demopolis there is an important occurrence of the white 

 rock extending along the left bank from a mile above the land- 

 ing to about 2 miles below, with an average height perhaps of 

 40 or 50 feet. (Plates IX and X.) The rock is remarkably 

 uniform in appearance and probably in composition (analysis 

 17.) At McDowell's the main bluff is on the right bank and 

 the rock is of great purity, as shown by analysis 16. The ex- 

 posures continue down to Pace's Landing, 9 miles below De- 

 mopolis, and beyond this the bluffs are much darker in color 

 and striped with lighter bands, characteristic of the strata of the 

 upper part of the formation. Thence down nearly to Moscow 

 occur the exposures of these upper beds. 



Above Demopolis at Arcola and Hatch's bluff the bluish 

 clayey limestones of the Selma division are seeni in force, with 

 the lowermost ledges of the Demopolis division the horse- 

 bone rock capping them. Two analyses of these varieties at 

 Hatches will show well the contrast in their chemical composi- 

 tion (analyses 19 and 20. (Plate XI.) 



From Demopolis eastward the line of the Southern Railway 

 is located on the outcrop of this white rock, at least as far as 

 Massillon, where it passes into the territory of the lower Selma 

 division. Two miles from Demopolis on this road is the cement 

 manufacturing plant of the Alabama Portland Cement Com- 

 pany, with six kilns in place. The quarry is on the opposite 

 side of the railroad track from the kilns, but only a. few hundred 

 feet distant. (This plant with quarry in the foreground is 

 shown in Plate XII.) The clay used is the residual clay from 

 the decomposition of the limestone, and is obtained from the 

 river bank a few yardls away. The composition of the rock and 

 of the clav used in the manufacture is shown by analyses 15, 18, 

 and 31, Table E, and I, Table G. A specimen taken from Knox 

 wood station, between the cement works and Demopolis station, 

 shows similar composition. The analyses below given (10, n, 

 6 



