Mesozoic and Ccenozoic Geology and PaUeontologij. 297 



1st. '' Blue hard pan,'' resting uuconformably on the surface of 

 the stratified rocks. This is a very compact mass of blue clay, marl 

 and sand, including great numbers of small, partial!}^ water-worn, 

 crushed and striated pebbles, principally fragments of blue limestone 

 and primitive rocks. It contains lime, so much as to effervesce with 

 acids, and to hasten vegetation when applied to land. Beside its strong 

 blue color, it is characterized by imbedded timber, dirt beds, leaves, 

 sticks, and what are called by well diggers "grape vines." It is so 

 solid as to be almost impervious to water, and is very difficult to ex- 

 cavate. 



2d. " Yellow hard pan," resting uuconformably on the stratified 

 rocks, and the " blue hard pan." This is a compact material, of a 

 dull yelloio color, with fewer stony fragments or pebbles, and less cal- 

 careous and more aluminous matter than the blue hard pan. It is not 

 quite as solid as the blue, more pervious to water, and contains more 

 and larger pieces of primitive rocks. The clays of the country, used 

 for bricks are principally of this bed. It forms a hard, stiff soil, 

 adapted for grass. The flat regions and savannas of the northwest 

 quarter of the State, are caused by the surface presence of this bed. 



3d. "Sand and gravel drift," containing granite bowlders (in small 

 numbers), of large size, and unconformable to Nos. 1 and 2, and the 

 other rocks. It exhibits little regularity of stratification, is composed 

 of inferior patches of coarse sand and gravel, intermingled at all in- 

 clinations, evidently the result of long continued and vigorous action 

 of water in rapid motion. The gravel is coarse, but much worn, 

 rounded and smooth, like the gravel beds of rapid streams. The por- 

 tion of earthy matter is about one half, of a reddish and yellowish col- 

 or, showing the presence of oxide of iron, and containing various pro- 

 portions of sand and clay. Almost ever}^ rock in the northern part 

 of America is represented in the gravel; but the greatest part by far 

 is from the underl3nng and adjacent strata. There are pebbles of 

 quartz, trap, granite, gneiss, conglomerate, limestones of all ages, iron 

 ore, slate, coal and sandstone. In this there has been found timber 

 but very rarel}'. 



4th. The " valley drift," composed principally of debris of the ad- 

 jacent rocks, and occupying the lower parts of the great valleys of drain- 

 age. It is more gravelly and less earthy, and the gravel is more of 

 local origin than in No. 3, while the beds of sand are less common. It 

 is in the " valley' drift'' or swamp mud that the bones of the mastodon 

 and other large animals are usuall}' found. 



