hundred feet in thickness, and are for the most part dis- 

 posed in a horizontal position. Its lower portion, where 

 it rests directly upon the Hudson river shales and sand- 

 stones, is ot a firmly compact nature, owing no doubt to 

 the lieavy pressure of the superincumbent mass ; but, as 

 we ascend in the series, its stratification begins to develop 

 itself, at first at distant intervals, but, on approaching the 

 surface, these' intervals are seen gradually to diminish in 

 thickness, until they terminate in layers so exceedingly 

 fine as scarcely to be discernible. 



Whenever this stratification first makes its appearance, 

 the separating material is a remarkably fine-grained pul- 

 verulent sand of a light silvery tinge, closely approxima- 

 ting to white : and this is continuous throughout the re- 

 maining portions of the formation. It is chiefly among 

 some of these seams of sand that the indurated calcareous 

 concretions, so frequently met with in this vicinity, origi- 

 nally derived their existence. These seams of sand, as 

 they approach the surface of the soil, are sometimes seen 

 to expand in such a manner as occasionally to admit a 

 stratum of a fine-grained yellowish sandy clay, from two to 

 four or more feet in thickness, the lower parts of which 

 not unfrequently become interstratified with fine layers of 

 the blue variety beneath, but most generally it is isolated 

 and compact in its texture. 



The general color of these clays is of a deep blue or 

 violet, closely approaching a neutral tint ; but as we as- 

 cend in the series, it is seen by degrees to lose its fine uni- 

 formity of shade, and at length to assume a more variega- 

 ted aspect. From the deep stone-blue beneath, this entire 

 mass, in its progress upward, exhibits among its numerous 

 strata almost all the other hues in nature, and in oft re- 

 peated alternations ; not blending imperceptibly one into 

 the other, as is so frequently seen, but so arranged in dis- 

 tinct bands as to present an appearance not unlike the 

 striped ribands on a lady's dress. 



