Bl'KKAC mi" STY. 



The swamp lands of Green river are also alluvial deposits. They are 

 .m ;issy marshes and imperfect peat moors and bogs, containing great 

 beds of black mud, muck, and impure peat. 



The Loess. The Illinois river bluffs, already referred to, are partially 

 made up of an imperfect loess deposit. These bluffs rise to a hight of 

 nearly one hundred and fifty feet, and display some of the charac- 

 teristics of the bluff or loess formation. The deposit is not as plainly 

 marked, however, as the marly, partially stratified clays and sands 

 along the Mississippi bluffs, about Fulton. Some of the steeper bluffs 

 present bald knobs, and light-colored marly clays exist along their 

 sides. Between Bureau Junction and Peru there are several places 

 where landslides have taken place, and the formation is more easily 

 recognizable. One of these is a marked feature in the landscape. 

 AT a distance, it presents the appearance of a heavy outcrop of a white 

 sandstone. A closer examination shows it to be a heavy bed of sliding, 

 crawling sand. It is a white, yellow-banded sand, marly in its composi- 

 tion, and exhibits the most marked lines and bauds of stratification. 

 The outcrop is about thirty feet in thickness. It may be found in the 

 side of the bluffs, near the railroad track, some three miles east of Tren- 

 ton. The caving sands have crawled down the hill almost to the rail- 

 road track. 



This loess formation thins out rapidly as it recedes from the bluffs, 

 and soon loses itself among the drift clays, with which it is closely as- 

 soeiated. These bluffs, for a part of the distance, in this county, show 

 no rocky outcrops along their bases or up their ravines, but are mostly 

 made up of loess and drift-clays, and sands. 



Drift. The usual yellow and blue clays of this part of the State lay 

 over this county in a thick deposit. The artesian well, at Princeton, 

 shows them to be about seventy-nine feet thick there, before rock was 

 struck. The record of that well shows that a thin bed of rock was 

 then struck, only three feet thick, and then a hard-pan clay was pene- 

 trated to the farther depth of one hundred and fourteen feet. There 

 may, however, be some mistake about this; the record was poorly kept. 

 It is more likely that the thin bed of rock was some detached mass 

 sticking in the drift clay, and that the real depth of these clays here is 

 about one hundred and ninety-three, instead of seventy-nine feet. 



Some of the higher ridges of the prairies contain finejy assorted 

 gravel beds. This is true of that portion of the county between 

 Sheffield and Tiskilwa. Some fair gravel beds are also opened along 

 the railroad northeast of Princeton. But these gravels are full of marly 

 clays and hard-pan. ]STo coarse gravel beds and fields of boulders were 

 noticed. Some detached boulders of black and flesh-colored granite 

 were noticed at a number of places on the surface of the prairie. No 



