170 GEOLOGICAL RErORT. [1283 



yellowish marls, somewhat chalky to the touch, without any visible 

 grains of greensand, and with casts only of small shells, which are 

 generally of a rust color, and form a very convenient criterion of 

 the quality of the marl ; for the more of these rust-colored casts of 

 shells it contains, the smaller, generally speaking, appears to bo 

 its pt of inert matter, and the bettor, of course, its adap- 



tation to agricultural purposes — all of which maybe studied to 

 advai S. of Calhoun Station, and in most 



of tl as dug between Canton and Jackson. 



The only complete analysis 1 h made of any marl of this character, 



refers to a specimen from the outcrop at Moody's Branch, at the foot of the 

 McNutt Mills, N. E. of Jackson (1204, Sec. 27) ; taken from stratum No. G of 

 the section quoted. It is yellowish-white, rather loose and porous, contains 

 little sand and but a few fossils — part of which, however, at this locality, retain 

 their shells. 



MARL FROM MOODY'S BRANCH, JACKSON. 



Insoluble Matter (white clay and fine silica) 37400 



Potash 445 



Soda 0.208 



Lime 28.S21 



Magnesia 1.407 



Peroxide of Iron, and Alumina 5.133 



Phosphoric Acid 0.25G 



Carbonic Acid, and Loss 23.084 



Water 3.24G 



100.000 

 The amount of Potash in this marl, it will be perceived, is much smaller than 

 in the greensand marls previously noticed; but it contains a large amount, 

 comparatively, of Phosphoric Acid, and as it is, is a vary eligible fertilizer, 

 though not so much a nutritive manure as those before mentioned. 



283. I have determined, indirectly, the amount of lime contained in two other 

 specimens, fair representatives of the marls of Madison and N. Minds. One is 

 a yellowish, calcareous clay, splitting in "flakes," quite hind to cut when dry, 

 containing some large oysters, but no small shells, and occasional crystals of 

 gypsum ; forms a plastic paste when wetted. Taken from a gully in the road- 

 side, 3 miles N. of Jackson. It effervesces weakly with acid, and the determi- 

 nation gave : 



Carbonate of Lime 17.47 L per cent. 



(or, pure Lime 9.804) 



Another specimen, taken from a bluff in Mr. Langley's field, near Jackson. 

 Light yellow, cleaving rather irregularly : feels chalky, and exhibits rusty casts 

 of small shells ; determination ga> 



Carbonate ot Lime 62.780 per cent. 



(or, pure Lime 35.230) 



This marl is probably quite similar in composition to that of Moody's Branch 

 (see above), but is richer in lime. Similar marls may be looked for all over N. 

 Hinds and ! on, and may ver} r generally be selected to suit the soils, 



according to their lightness or heaviness. As they do not seem to contain iron 

 pyrites, their exposure to the atmosphere previous to plowing under, will only 

 be necessary in so far as it favors their pulverization. 



The lower blue strata at Jackson — (Nos. 4 and 5, Sec. 27, f 204) 



