302 NATURAL HISTORY BULLETIN. 



The thickness of the loess at Natchez has been variously 

 reported. L,yell§ gave it as sixty feet, but he probably in- 

 cluded the brown loam; Hilgard[| reported its average thick- 

 ness as between twenty-five and thirty-five feet; McGeeTl states 

 it as ten to fifty feet; while Capt. C. W. Babbit, of Natchez, 

 an experienced surveyor and civil engineer, who has had much 

 to do with excavations, assured the writer that it nowhere ex- 

 ceeded twenty-five feet in thickness. The writer's own meas- 

 urements showed a maximum thickness of about thirty feet, 

 though in the exposures numbered 29 and 31 on the map, it 

 seemed to be much more, but accurate measurements could 

 not be made. It is probable that the front portion of the bluff 

 had slipped in part and thus exaggerated the apparent thick- 

 ness of the loess. Such slipping was well illustrated opposite 

 exposure No. 12 at x. A mass of loess about 25 feet high, 15 

 feet wide and 165 feet long, slipped vertically about two feet. 

 Subsequent erosion of the face of the bluff at one end of the 

 mass made it appear as though the mass extended from the 

 original upper surface to the new lower surface, — a distance 

 of about 27 feet. The underlying Orange sands, which are 

 easily washed out, always make such faults possible, and con- 

 sequently care must be exercised in making measurements on 

 the exposed faces of bluffs. 



The material of the deposit possesses typical loess charac- 

 ters. It is a fine yellow or slightly bluish clay, showing a 

 tendency toward vertical cleavage, containing lime nodules 

 and iron tubules, occurring on higher grounds, and abund- 

 antly fossiliferous. Its hypsometric distribution is also like 

 that of the northern loess, for it mantles the hills, and varies 

 but little in depth. This is well illustrated in Plate III. In 

 many respects it is strikingly like the loess along the Missouri 

 river, being somewhat coarser and containing more lime, and 

 consequently eroding less readily, than the loess of the upper 

 Mississippi valley in Iowa and Illinois. But for the under- 



>i Prin. of Geology, vol. I, p. 460. 

 liP. 313, 1. c. 

 IP. 397, 1. c. 



