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GEOLOGY OF THE FIRST DISTRICT. 
Boulders and pebbles of the kind alluded to in the above references, are scattered over 
every township in the valley of the Hudson, to Long and Staten islands. They seem to have 
been derived from Columbia county, and the continuation of the same rock in Massachusetts 
and Vermont; and they contain the pulverulent earthy oxide of manganese, that has remained 
in the cavities of the slate and quartz, where the brown spar has been decomposed. The wad 
has been deposited in low grounds, and at the outlets of swamps, and is more or less mixed 
with bog ore. 
It is important that localities of the oxide of manganese should be discovered, from which 
that mineral may be procured and used in the manufacture of bleaching powder, of glass, etc. 
The Bennington mines have ceased to supply the demands of commerce, and most of that 
now used is imported from Germany. Perhaps some of the localities in Austerlitz and Hills¬ 
dale may be employed. The manufacturers who use this material in their workshops and 
factories, could soon ascertain if they could use it with advantage. 
11. Carbonate of Copper. 
The carbonate of copper has been discovered only in minute quantities in the First Geologi¬ 
cal District, and the localities observed may be found in the Mineralogical Report by Prof. L. 
C. Beck. 
12. Alluvial Sandstones and Conglomerates. 
These are mostly formed by the cementing action of the oxide of iron, and the carbonate 
of lime, which are deposited from water in the interstices of the grains of sand and gravel, in 
unconsolidated beds of these materials. The rocks thus formed by the action of present 
causes are not extensive, and are found in but few places. The filtering of clay in suspension 
in water, is another cause tending to form solid aggregates; but they have little firmness, 
yielding readily to the action of water. 
At Broad-meadow point, called also Iron point, two or three miles east of Riverhead in 
Suffolk county, is a recent sandstone in thick solid masses. In some places it is mostly com¬ 
posed of the oxide of iron, and may be called hog ore. Generally it is a sandstone, the 
grains of which are cemented by a large proportion of oxide of iron. 
A similar recent sandstone may be seen in the tertiary sand cliffs between Roanoke point 
and Mattituck inlet, on the north coast of Long island. 
Nodular masses of iron pyrites, in one of the gravel and pebble beds of the tertiary on 
Long island, are common, and by their decomposition form brown hematite. This envelopes 
the surrounding bodies, which serve as nuclei, and cements them together into solid rocky 
masses of sandstone and conglomerate. When nodules of clay or of decomposing rock are 
thus enveloped, geodes are formed, some of which contain loose sand, others lumps of clay, 
and others are mostly filled with water. All these facts may be seen, illustrated at the high 
cliff of tertiary on the northeast side of Lloyd’s neck, in Huntington, on Long island. Two 
of the hollow geodes that were filled with water, and found at this place, may be seen in the 
