E. W. Hilgard on the Quaternary of Mississippi. 813 
Oran e Sand, are coéxtensive with those in which fossil wood, 
either silicified (when imbedded in siliceous sands) or lignitized, 
Strata. It is not at all unusual to find trunks of silicified wood 
imbedded partly in the unchanged lignitic strata, partly in the 
range Sand; the portion contained in the latter being nearly 
or wholly deprived of carbon, while the part imbedded in the 
lignitic material is, if at all silicified, of an ebony tint, and often 
Contains pyrites (§ 26, ad finem). A 
While, therefore, I admit the possibility of a further specific 
determination of these silicified trunks assigning to the Orange 
and some peculiar species, I am convinced that the greater part, 
if not all of this fossil is derived from the underlying strata, 
appropriation and re-deposition of their materials with the irreg- 
Warity of arrangement consequent upon the alternate existence 
of currents, eddies, slack water and counter-currents, in one and 
the same place. : ; 
he geographical distribution of this formation, as well as the 
wafean : strata are suffi- 
