342 
GEOLOGY OF THE FOURTH DISTRICT. 
166 . 
Alluvial hills and terraces on the Conhocton valley, as seen from Liberty corners. From a sketch bj Mrs. Haia. 
CHAPTER XIV. 
MODERN SUPERFICIAL DEPOSITS. 
After the period of the superficial deposits just described, and when the surface had be¬ 
come permanently elevated above the ocean, its inequalities would give origin to broad lakes 
and rivers, discharging themselves into the surrounding sea. By any irregular motion attend¬ 
ing the farther elevation of the land, and even from the accumulation of water alone, the bar¬ 
riers of these lakes might be broken down, their beds deepened, and vast quantities of detritus 
carried to the lower plains, or into lakes or rivers at a lower elevation. That such has been 
the condition of the whole of New-York, will admit of demonstrative proof, and the details 
of the various modifications of this modern period would occupy many chapters. In many 
instances it requires much careful examination to separate the products of this period from 
those of previous ones, and also to recognize the different ages of modern deposits ; for 
these again are, among themselves, referable to distinct epochs. We can only select a few 
well defined examples, and such as are produced by causes that will at once be recognized; 
leaving a consideration of the whole subject, and the various and successive changes, to some 
future opportunity. 
