268 
AGRICULTURAL GEOLOGY. — NO. 4. 
AGRICULTURAL GEOLOGY.— No. 4. 
In adverting to clay-slate rock and soils, at 
the close of our last number, (p, 172,) we ap- 
proach a series of minerals, which, for charac- 
ter and extent, differ exceedingly on this conti- 
nent, from any of the like in Europe; and, as 
when treating of this series, we touch upon those 
which underlie the greater part of this state, 
and which have, on that account, received the 
name of the " New- York system" of rocks, the 
necessity of dealing with it somewhat fully is 
imposed upon us. 
In western Europe, the rocks which lie above 
the mica slate, and below the old red sandstone, 
are comparatively well marked, and easily re- 
cognised in their general appearance. They 
consist of a series of slates and flag stones, some- 
times dark colored and soft, and occasionally 
splitting irregularly, sometimes affording beau- 
tifully thai and perfect slates, of great superfi- 
cial dimensions. Such are the slates from Ban- 
gor, in Wales, and Cumberland, in England. 
These are generally the lowest beds, those 
higher up losing that useful property called 
cleavage. The beds lying over those which 
furnish these slates, generally yield good flag 
stones. Above these, lie beds of stone mostly 
of a flinty and silicious character, which still 
have the slaty cleavage, and yield good corn-mill 
and grindstones. This series of rocks is the 
first which shows any trace of life having ex- 
isted at the time it was formed. The traces are 
the remains of stalks of corals, a few scales of 
fish, and some thin fibres of seaweed of 
simple form. They are distinguished from the 
rock systems previously described, in not pre- 
senting well-marked evidences of having been 
at one time melted, but rather show that they 
constituted the bottom of an ocean of great 
depth, in which the clay, mud, and sand had 
ample time to settle down evenly in alternate 
layers, and going on for a long period of time, 
and occupying a great extent of sea bottom, and 
shell fish, corals, or other animals dying during 
the period, would become imbedded in the 
mass. Thus, kept in some degree from the de- 
composing action of the air and water, they 
would be handed down to us as the remains of 
the inhabitants of a world in times long gone 
by. 
After the lowest beds were deposited, and be- 
fore the uppermost or last were settled down, 
volcanic action and upheaval occurred from 
below, bending, cracking, and elevating the 
oldest beds at various angles. Hence, it is, that 
when the whole was finally upraised from the 
ocean deep, these upheavals appeared as very 
high and rugged hills with sharp peaks and 
shoulders, the characteristics of a slate country. 
The bending and cracking were produced by 
melted greenstone and trap, endeavoring to find 
a vent upwards, and forcing all above before it. 
It cooled down, however, before passing 
through the thickness of slate, and hence forms 
the walls or dykes, or trap, or greenstone met 
with in slate. The greenstone brought up 
.metallic, copper and tin, in great abundance, 
and deposited them in the sides of the dykes; 
the oldest beds of slate being those rocks where 
these two metals are found most abundant. The 
upper beds of clay slate have not these metals, 
and but few dykes of greenstone ; but in their 
place, beds of granular, white limestone occur, 
with veins of galena, or lead ore. The topmost 
beds of the series contain no metals, and con- 
sist of sandstone and shaly slate, with beds of 
coralline and shelly limestone of a dark color. 
Occasionally, beds of pebbles cemented by 
paste, into a rock, and termed conglomerate, are 
met with, until at last we come to these beds of 
dark- red sandstone, of which our city churches 
are built, and which is known as the old red 
sandstone. Here terminates the slate rocks. 
They are not equally well exhibited in every 
country. Thus the lowest or metallic beds are 
better developed in England than here, the mid- 
dle series in central Europe, while the topmost 
series, or those which have no metal, are best seen 
in those states, being close to the sandstone beds, 
it partakes much of that character, and has lost, 
to some extent, the slaty cleavage. Such rocks 
were termed grauwacke, in Europe, but from their 
extent and importance in this state, they have 
been called the New-York system of rocks. 
They occupy almost the whole centre and west 
of the state, and are the most fertile spots known. 
The salines, the water limes, and the gypsum 
beds belong to this class of rocks, and they 
stretch from Lake Ontario to the Pennsylvania 
border, where they dip down south under the 
old red sandstone of the boi'der counties. The 
various beds described have received names 
from the localities where the best-marked spec- 
imens'were found. Thus Potsdam sandstone, 
Trenton limestone, Utica slate, Hudson-River 
slate, Medina sandstone, Niagara group, Onon- 
daga salt group, Portage and Chemung slates 
are familiar names. 
The inclination of the New-York system of 
rocks is very slight in the central counties, ly- 
ing at an angle sloping south eight or ten de- 
grees; hence there is but little inequality of the 
ground, no mountain chains, and the land fa- 
vorably disposed for tillage. It is different in 
the east of this state, as along the Hudson River, 
where the earlier deposited beds of slate lie on 
primary rocks; their upheavals are abundant, 
and the land too stony and rugged for profita- 
ble cultivation. Again, along the Pennsylvania 
line, the newest beds are found joining the sand- 
stone, and these, also, have been upraised to a 
high angle, and produce the picturesque scenery 
along the Erie Railroad. The soil of this ex- 
tensive tract of country is as varied as the rock 
itself. Sometimes it is altogether derived from 
the slate rock, and then its character is a stiff 
clay; but this only occurs in a few places, and 
its general composition varies from a loose sand 
to a marly clay. How comes this difference of 
soil? 
We must recollect that after the rocks were 
deposited and consolidated, they lay underneath 
the deep water of the sea, with a strong current 
flowing southerly, tending a little eastward. 
If any soil ever formed on the surface of these 
rocks, it was swept away by the force of the 
