4 
GEOLOGY OF THE FIRST DISTRICT. 
CHAPTER 11. 
QUATERNARY SYSTEM. 
PRELIMINARY REMARKS. 
This system is intended to embrace the alluvial, and all those accumulations of matter 
above the newer tertiary. It is necessary to adopt this grouping, in consequence of the 
absence of organic remains, and all other sources from which specific distinctions can be 
drawn. The differences of age and circumstances of deposition are evident, and these deposits 
will be discussed as far as practicable in their natural order under the following divisions, viz : 
1. Alluvial Division ; 
2. Quaternary Division; 
3. Drift Division. 
1. ALLUVIAL DIVISION. 
These alluvial deposits are in constant process of formation, by a great variety of causes 
in action at the present time. 
The phenomena of the alluvial deposits of the district are of much practical importance to 
the State, as they increase or lessen the value of particular situations. The phenomena of 
land-slides, sand-dunes, or hills of drifting sands ; the formation of peat, shell-marl, bog iron- 
ore, and tufa deposits from springs ; the washing away of the land so as to form banks, bars 
and shoals in our rivers and bays, and along our coast, are the most important. 
Alluvial deposits open one of the most interesting and important fields of geological research. 
In them we study present causes, and are enabled to investigate all those natural changes 
which are now in progress, and which serve to modify the present surface of the earth. They 
also enable us to trace the action of similar causes in former times, when the most of the 
rocks with which we are acquainted were formed. 
Fluviatile Alluvions. 
In the Hudson are many alluvial islands between the mouth of the Mohawk and Catskill. 
These islands, and the sandbars and mud-flats, have been increasing in elevation and extent 
