ONONDAGA-SALT GROUP. 
153 
III. HELDERBERG DIVISION. 
Remarks descriptive of the appearance of the Helderberg range from the hills east of 
Greenbush , and explanatory of Plate I.—This range is remarkable for the succession of ter¬ 
races as it rises from its eastern slope, and for the offsets after it has attained its height 
towards the north or valley of the Mohawk. Each terrace marks the position of the 
several limestones, which, being harder than the shales, form permanent tables extending 
beyond the limits of the shales, that are confined to an outcropping and nearly horizontal 
edge. The slope or dip is southwest, and the range rises from beneath the Catskill moun¬ 
tains, which rise up in dome-shaped segments upon the left. We see, in this view, merely 
the eastern slope: to the west there is a succession of minor ranges, separated from each 
other by north and south valleys. The Hudson-river series appears in the foreground, 
and are colored purple ; the limestones are colored blue, the shales a light drab, and the 
Catskill sandstones (which are the superior rocks, and beneath which all disappear) a light 
brown. 
§ 1. Onondaga-salt group. 
If we estimate the importance of a group or series of rocks by the amount of useful 
materials it furnishes, then this group is certainly one of considerable consequence. This 
will be admitted, probably, when it is stated that it furnishes most, if not all the plaster 
used in Western New-York, and much that is used in the New-England States. It un¬ 
doubtedly gives origin to the brine springs from which a large proportion of our salt is 
made, and from which an immense revenue is derived by the State. Besides these im¬ 
portant considerations, the rocks themselves form by decomposition an excellent soil, and 
the belt over which the group prevails is one of the best agricultural districts in the State 
of New-York. Without doubt, then, if this view is the true one, this group becomes both 
geologically and economically important. Its relations and associations are inquiries of 
considerable moment; for it is essential that its position in the series should be well un¬ 
derstood, and the nature of the deposits forming it well determined. Such being our 
opinion in regard to it, we proceed to describe the series in the same order which has been 
observed in the preceding groups. 
The specific characters which distinguish this group from the preceding , and the different 
members which form it. Leaving out of view those characters which are derived from its 
organic remains, we find that it is composed in the ascending order, of, 
1. A red shaly fissile mass with green spots and a few bands, constantly breaking down under the 
action of atmospheric agents. 
2. Green shale, rather massive, in which plaster beds are embraced, and which also contain casts of 
crystals of hopper-shaped cavities in which common salt once existed. 
[Agricultural Report.] 20 
