THICKNESS AND CHARACTER OF THE SILT. 297 



The thickness of the silt on uplands outside the limits of the drift is 

 even less than on the drift, thoug-h it probably falls short but a foot or two. 

 The estimates are mainly from exposures on slopes, there being few oppor- 

 tunities to learn its thickness on the level upland. It should be borne in 

 mind, also, that the country outside the limits of glaciation is generally much 

 more uneven than in the glaciated tracts, and that flat areas such as would 

 hold the silt in its full thickness are comparatively rare. The silt is seldom 

 preserved in the Ohio Valley, the exposure at Parkersburg being- the most 

 conspicuous instance noted. In the northern part of the city it covers au 

 island-like hill which stands about 175 feet above the river, and it there has 

 a thickness of 12 to 15 feet and a porous texture similar to the loess along 

 the valleys farther west. 



In the abandoned valley of the Kanawha, leading from St. Albans, 

 W. Va., to Huntington, known as Teays Valley, there is apparently a thin 

 bed of the silt under discussion, capping a thick deposit of silt of different 

 color. The thickness is only 5 or 6 feet, or but little greater than on the 

 bordering uplands. 



The deposits in the Beaver and Monongahela valleys which are con- 

 jectured to be of this age are only a few feet in depth, those on the Beaver 

 being 5 or 6 feet and those on the Monongahela but little thicker. 



CHARACTERISTICS. 



Color. — The color of the silt is a distinguishing characteristic, for it is in 

 striking contrast with both the underlying till and with the residuary clay, 

 and is remarkably uniform throughout its extent in this region. It is 

 generally of a pale yellow or ashy color from top to bottom, the soil as 

 well as the subsoil being pale and light colored. For this reason it is 

 widely known as "white clay." In parts of southern Ohio and southeastern 

 Indiana this deposit has given rise to a black soil. This is found mainly in 

 exceptionally flat portions of the uplands, and does not prevail very exten- 

 sively there, the level tracts being usually characterized by a very light- 

 colored soil. 



Texture. — Tlic uaiue silt indicates that this deposit is of fine texture. 

 Ordinarily it contains no grains or rock fragments sufficiently coarse to be 

 detected by the naked eye, but in a few places occasional small pebbles 

 have been noted in it, usuall}' near the bottom of the deposit. The rarity 

 of these pebbles raises the suspicion that they may not be normal tq the 



