302 T. 0. MABRY 



and in the latter into calcareous and ferruginous nodules. At 

 the contact plane of the former with older formations — the 

 Lafayette around Oxford, or the Northern Lignitic a few miles 

 east — there are frequently selvedges of "hardpan," or ferru- 

 ginous sandstone, sometimes of considerable size, and occasion- 

 ally containing a high percentage of iron. These are not to be 

 confounded with similar "iron ores " of the Lafayette. That the 

 loess has suffered less alteration than the loam is evident. The 

 present difference between the two may be due partly to 

 original difference in chemical composition and physical tex- 

 ture, but more largely I think to a difference in degree in sub- 

 sequent alteration. The latter may be attributed to the differ- 

 ence in thickness of the two, which would both give to the loam 

 a higher percentage of organic matter (derived from older 

 soils), which on decomposition would furnish abundant solvent 

 for its soluble constituents, and also allow a freer circulation of 

 water for the accomplishment of the decomposition of putresci- 

 ble matter and consequent leaching of the loam. 



The roots of existing plants, too, may penetrate through the 

 loam as they could not always the loess. But the Memphis 

 sections would seem to indicate, also, original local differences 

 in chemical composition and physical texture. 



T. O. Mabry. 



University of Mississippi. 



