PIKE COUNTY. 37 



been transported, or drifted, to the region they now occupy. This appears to 

 have been accomplished, mainly by currents trending southwardly, for we find 

 in the drift deposits, water-worn boulders of all the rock formations, outcropping 

 over an area of four or five hundred miles to the northward, as far, at least, as 

 the northern shores of the great lakes, from whence the granitic, sienitic, and 

 igneous boulders have come. Over a large portion of this county, especially 

 adjacent to the river bluffs on either side of the county, the drift is rarely ex- 

 posed, from the thickness of the overlying beds of Loess, which covers it to 

 the depth of from ten to fifty feet. In the central portions, it is more accessible, 

 and is penetrated in digging wells, and all other excavations below the subsoil 

 of the surface. Heavy beds of drift material cover the surface, overlying the 

 Keokuk limestones in the vicinity of Perry, and extend southward through the 

 central portions of the county, with a variable thickness ranging from twenty 

 to forty feet, or more. They are composed mainly of brown and yellow grav- 

 elly clays, which usually become bluish gray towards the bottom, and enclose 

 rounded boulders of metamorphic and igneous rocks, as well as those derived 

 from the limestones and sandstones that constitute the paleozoic strata of our 

 own and the adjacent States. Towards the river bluffs, the drift deposits are not 

 so thick, and at some points along the summit of the bluffs, they are wanting 

 altogether, and the Loess rests directly upon the limestones. At many points 

 in the State, beds of stratified sand and clay are found beneath the Drift, over- 

 laid by the ancient soil which covered the surface anterior to the Drift period 

 but no shafts have been sunk, or other excavations made, so far as I am aware, 

 in this county, deep enough to determine whether these Post Tertiary beds 

 exist here. It is quite probable they will be found in the central and northern 

 portions of the county, as they are known to exist in the adjoining county on 

 the north. At the base of the Drift deposits, in the vicinity of Barry, there is 

 a bed of clean, yellow flint gravel, that is partly cemented by the oxide of iron 

 into a ferruginous conglomerate, like that on the Ohio river, in Massac county, 

 which has been considered as of Tertiary age. It was scarcely more than a 

 foot in thickness where we saw it exposed. 



Economical Geology* 



Building Stone. Pike county has an abundant supply of excellent building 

 stone, which may be obtained from all the principal limestones that outcrop 

 within its borders. The Niagara limestone, in the vicinity of Pleasant Hill, 

 furnishes a buff magnesian rock, in very regular beds, fully equal in quality to 

 thnt afforded by the same beds atGrafton end Joliet. The upper ten or twelve 

 feet of this formation is of this character, while the lower strata are of a gray 

 color, contain less magnesia in their composition, and, although a durable stone, 



