82 
GEOLOGY OF THE FIRST DISTRICT. 
These localities in Barnegat and New-Lebanon are on the Barnegat limestone, which is, 
in some places, modified as a metamorphic rock. 
The cause of the deposition of carbonate of lime to form stalactites, stalagmites, tufa, sinter, 
tufaceous marl, and incrustations, is, that the carbonic acid, which by its excess held the 
carbonate of lime in solution while in the earth, passes off when it flows from the surface, 
where the water can contain only an equal volume of the gas at the ordinary pressure of the 
atmosphere ; or by partial evaporation of the water, a deposition follows equal to the quantity 
that the evaporated water held in solution. In most instances, both these causes are com¬ 
bined to produce the results. Rain water always contains some carbonic acid, and although 
its solvent power is small upon the limestones, it is nevertheless very perceptible in the course 
of ages upon the most dense and compact limestone rocks. Water that percolates into the 
earth acquires more carbonic acid, and its solvent power is still more distinct in limestone 
caves, most of which have been principally formed by the solvent power of carbonic acid in 
water. 
Clay Balls, and Calcareous Concretions. 
There is another class of calcareous concretions, commonly found in the tertiary and qua¬ 
ternary clay beds, but which are of alluvial formation. One division of them seems to be 
formed by segregation, like septaria and the various nodular masses imbedded in limestone, 
slate, and other rocks. They present a great variety of imitative forms; rarely spherical, 
except when grouped in botryoidal masses, as they sometimes occur in the clay and sandy 
clay beds around Newburgh bay ; but generally flattened ovoidal, digitated, and more similar 
in form to the various shapes of cakes made for children, that we see in the baker’s shops. 
They are formed between the layers of clay, at considerable depths from the horizontal sur¬ 
face ; but I do not know of an instance in which they have been found at any considerable 
depth, in digging wells or making excavations, at a distance from the edge of a clay hank. 
They are commonly found where clay beds are crumbling or washing away, and they seem 
to form near the edges of the layers of the clay, where they are exposed to the weather. They 
are formed of the clay, but contain carbonate of lime suflicient to indurate them, and some¬ 
times to slake when burned. At the brick-yards where these clay balls and concretions occur, 
they pick them out of the clay before grinding it; else the bricks will be of inferior quality, 
and burst to pieces when wet, in consequence of the slaking and expansion of the lime. 
The other division is formed by organic causes. They are of almost all the shapes of a 
tubular, flattened ovoidal or annulated form, and almost universally have a hole through them ; 
some not larger than a fine needle, others of the size of the finger or of the arm. They are 
formed in and between the layers of the clay, but never, it is believed, below the depth to 
which the roots of plants penetrate. They seem to be formed by the roots of plants absorb¬ 
ing the water, and perhaps the carbonic acid of the water in the earth, and rejecting the carbo¬ 
nate of lime that was held in solution by one or both. This, by its deposition, remains around 
the root or fibre, and indurates the clay. I have seen many examples in the Hudson valley 
