11454,455, 4c C, 457, 458J tertiary and post-tertiary marls. 233 



Vicksburg («[220, 278), Byram Station (1280), Falling Creek (V218, 290), and 

 numerous other localities. 



454. As in the case of the cretaceous marls, the green and blue marls of the 

 Tertiary are, as a general thing, richer in potash and poorer in lime, than the 

 White marls. The former are therefore to be considered rather more in the 

 light of true m 'in arcs, the latter, rather as stimulants. None of them, however, 

 are entirely void of potash ; the white marls of Rankin and Hinds counties 

 average from two-tenths to five-tenths of a per cent, while the greensand marls 

 usually range between 3 ( and 1% percent, of the same substance.* (For 

 analyses of these marls, see Geological Report, 1T278, 280, 282, 283, 285, 202). 

 As for the yellowish-white or gray clay marls of Madison and N. Hinds, such as 

 are common on the road from Jackson to Canton (if 281), no complete analyses 

 showing their character and quality have as yet been made (for partial analyses 

 see 1f283). There is no doubt, however, that if judiciously selected, they will 

 be of great service on the yellow loam lands of the counties mentioned. 



455 III. Clay Marls of the upper, fresh-(pv brackish-) water Tertiary, or Grand 

 Gulf Group (If 230, ff.) of South Mississippi. They are found interspersed in 

 patches, sometimes of very limited extent, in the beds of gray, green and blue 

 clays which occur, alternating with sandstone ledges, in the whole region S. of 

 that which furnishes the mirls described under No. 2 ; or south of a scolloped 

 line extending from Grand Gulf, via Clinton, Brandon and Raleigh to Winches- 

 ter, in Wayne county, and thence into Alabama (see map, and 1|'29G to 302). 



The materials of this formation appear to be very generally rich both in 

 Magnesia and Potash (if 231), although the eye cannot detect in them any 

 grains of greensand. The analyses thus far made (If 296, 300, 302) show from 

 one to two per cent, of Magnesia, seven-tenths to one-fourth per cent, of Potash ; 

 and from 1 % to 22 per cent, of Carbonate of Lime ; not, however, any large 

 amount of Phosphoric and Sulphuric acids. Their most usual character is that 

 of heavy, gray or bluish clays, which, when rich in lime, contain irregular veins, 

 nests or layers of white calcareous concretions, which when wet, are sometimes 

 quite soft and friable ; but so far as my observations reach, contain traces only 

 of fossils — no distinct shells, as do the marls of the other formations. 



There occur also, in this formation, materials not sufficiently calcareous to 

 claim the name of marls proper, yet still likely to prove useful as fertilizers 

 when conveniently situated. Concerning these, as well as the localities of 

 occurrence of the clay marls mentioned, see Geological Report. If 295, 203. 



456. The deposits of disintegrated shells imbedded in black clay, sometimes 

 found on the streams of the Coast (If248, 249), have not as yet been saticfact) 

 rily examined. Particulars concerning them will be found in the place above 

 referred to, as well as under the head of the Sea-Coast Counties. 



457. IV. Fresh water marls, of more modern age than the Tertiary. 

 Among these may be classed the calcareous silt or loam which forms the main 



body of the hills of the Southern River Counties ; and under the latter head will 

 be found an analysis, as well as a full discussion of the merits of this material. 



Limited deposits of a character not unlike the above, are sometimes found in 

 the sites of lakes in the Mississippi bottom, as described by Prof. Wailes (First 

 Report, p. 231), under the head of "Lake Marl." Being unacquainted with the 

 mode and extent of occurrence, as well as with the composition of this material, 

 I have nothing to add to what is said in the passage referred to. 



458. Marling. — As to the mode of applying the marls just described, little 

 need be added to the general rules already given (see also under the head of 

 Agricultural Chemistry, what is said concerning the use of lime, If 368, ff.) 



*It may be necessary in this connection to call attention to the fact that the 

 analyses of New Jersey greensand, which show it to contain ten per cent, of 

 potash (as is frequently quoted), refer, not to the whole, average mass of materi- 

 als which is used in practice, but to the picked, pure grains of greensand proper 

 (glauconite). 



