CAKBONIFEROUS SYSTEM. 193 



Bed No. 2, is merely a layer of compact limestone, everywhere crowded with 

 shells, principally Ghonetes. It averages about six inches in thickness, and caps 

 the sandy bed No. 1 with marked distinctness. 



Bed No. 3, is another mere band of limestone only about three inches in 

 thickness, but is very distinct on account of its oolitic structure, and principally 

 interesting as showing the tendency of the limestones of this formation to assume 

 that peculiar structure, as will be shown farther on. 



Bed No. 4, reaches a maximum thickness near Burlington of twelve feet. It is 

 dark grey compact limestone, sometimes slightly arenaceous. It breaks up into 

 small fragments upon exposure, and is very fragmentary, even where not exposed 

 to the atmosphere. 



Bed No. 5, is a fine grained, yellowish sandstone, so much like some parts of 

 No. 1, that it is impossible to distinguish them apart, unless seen in connection 

 with its associated beds. This bed at Burlington reaches a maximum thickness 

 of seven feet, and is often found crowded with casts of fossil shells, embracing 

 many genera and species; some of which are peculiar to that bed alone, although 

 a majority of the fossils range vertically through the entire formation without 

 interruption. The fossils of this bed, like those of No. 1, are principally 

 Lamellibrancliiates and Brachiopods. They are also generally of small size ; yet 

 adult. 



Bed No. 6, is a light gray oolitic limestone, very uniform in its lithological cha- 

 racters, and has a thickness in the vicinity of Burlington, varying from two to 

 four feet. 



Bed No. 7, is composed of impure limestone, sometimes magnesian, and at Bnr- 

 lington it passes so gradually into the Lower Burlington limestone that it is difficult 

 to say where the distinctive characters, whether lithological or palaeontological, 

 of one formation end and those of the other begin. There are three or four feet 

 in thickness here, however, that cannot be referred to any other than the Kinder- 

 hook beds, however closely it may be joined to the strata of the Burlington 

 limestone. This portion, as well as all the other beds beneath it, disintegrate 

 more readily than the true Burlington limestone which rests upon it ; so that the 

 ledges of the last named formation are often found jutting over the mural face 

 of the Kinderhook beds, which gradually give way by disintegration beneath 

 them. 



The accompanying sketch, taken near Starr's Mill, on Flint 

 creek, three miles northwest from Burlington, shows the 

 general aspect of the two formations at their junction. The 

 projecting strata here represented are those of the Burlington 

 limestone, the real base of which can be distinctly traced in 

 the sketch. All beneath the projecting mass belongs to the 

 Kinderhook beds. Beneath these overhanging layers, which 

 project sometimes as much as twenty feet, no rain can reach, 

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