STATi; IIOR'I'ICULTURAL SOCIETY. ^43 



ferencc of (.•Icvalion uf llic siirhicc hum ihc adjat cnt level of the 



country. 



At Rock Island is the point of crossing of another similar though 

 lesser axis; at the mouth of Illinois river is another; in Monroe county — 

 at Grand Tower and at Thebes are others; all of which cross the State 

 in a southeasterly direction. Besides these principal ones are lesser un- 

 dulations lying between them. 



All these axes have left tilled up more or less the strata of the Si- 

 lurian, Devonian, and Carboniferous ibrmations, bringing various quali- 

 ties of sandstones, limestones, and clays above the previous general level. 

 This was prior to the drift period, and it is very apparent that the area 

 of the State of Illinois did not then present as even a surface as now. The 

 drift period was not one continued o\ erwhelming movement of a great 

 mass of material, l)ut the evidences afforded by its depositions are that 

 it was long continued and of varying action, sometimes with great force 

 like a glacier, moving everything before it, and denuding the surface 

 under it, plowing down the elevated portions, then with long periods of 

 o]jen water and (|uiet depositions of clayey matter in water almost clear, 

 willi movements of icebergs in the same manner as now noticed in the 

 ocean, dropping the solid matter carried along in the form of boulders, 

 gravel, and <Tay as the ice melted. 



The effect of all this was the leveling down of the elevated por- 

 tions and moving them forward in a southerly direction, mixing the 

 fragments of the Laureniian clay slates of British America, the boulders 

 of granite and other hard rocks of the lake origin with the Silurian 

 limestones, clays, and silicious rocks of Wisconsin and Northern Illinois, 

 the carboniferous limestones, clays, and sandstones of Northern and 

 Central Illinois, all ground together as in a mortar, llien again mixed 

 with the erosions of Devonian and Carboniferous formations ol Central 

 and Southern Illinois. Much of the material seems to have been taken 

 u]} and moved forward many times. As we go south examining all that 

 belongs to the drift we lincl the boulders decrease in size, then in num- 

 ber, and tile gravel beds are finer and fewer, with a general tendency 

 of the soil to a finer state of division. 



It was formerly considered that the ridge on which Pana stands was 

 the southern limit of granite boulders; 1 have found them on the toj) 

 of the high ridge of Southern Illinois — the Cobden and Makanda hill — 

 though never larger than three or four inches in diameter. 



While in this general way the origin of the great mass has been 

 accounted for, let us look at some of the local differences. 



Near the northern line of the State considerable gravelly soil is 

 found east of the more elevated region. One hundred to one hundred 

 and fifty miles south, gravel beds are interstrali-fied in the blue clays, af- 

 fording reliable water-beds for wells. Sometimes large areas are sandy, 

 as in the vicinity of Morris, Onarga, and Hennepin. I'his is from the 

 adjacent outcropping sandstones of the coal measures and the St. Pe- 

 ter's sandstone. In the case of the Onarga region it is associated with 



