ALLUVIAL DIVISION. 
83 
clay beds, where these clay balls were still penetrated by the living roots and fibres of trees 
and plants ; others, where they were more or less decayed, but still showing the bark or the 
woody fibre, or both (generally the former); and others, where the cavity alone remained, 
without any appearance of organization in the cavity, except that in some instances the impres¬ 
sion of the root remained where the clay was highly indurated. I have seen similar concre¬ 
tions, with holes through them, in the valley of the. Connecticut about Middletown; and it is 
believed that they are common in clay beds, where the clay contains some carbonate of lime. 
The localities in the valley of the Hudson and its tributaries are so numerous, that it is unne¬ 
cessary to specify more than a few, where they are most easily accessible for the greatest 
number of observers. The clay beds about Albany, wherever excavated, show them more 
or less abundantly, and of all the varieties mentioned. 
The clay beds at and near Schoharie, Schoharie county, contain many of the common 
concretions. Between Lower Redhook and Rhinebeck landings, near the shore of the Hud¬ 
son, I saw an oak tree that had been uprooted by the wind, with hundreds of these annular, 
tubular, and discoidal concretions dangling from its smaller roots and fibrous rootlets. They 
are not uncommon about Hudson, Poughkeepsie, Hyde-Park, Fishkill, and throughout the 
clay formation of the Hudson and its main tributaries, and Lake Champlain. 
Various explanations and hypotheses have been offered to account for the origin of these 
concretions, which often assume the forms of art, or forms that might be supposed the result 
of organization ; but after a careful examination of the facts in many places, I believe they 
may be referred to the causes before mentioned, viz. to segregation, or the attraction by which 
similar particles are brought together in masses, in any heterogeneous matter in which they 
may be diffused; to excretion from the roots of plants ; or to the deposition of the calcareous 
matter held in solution by the water surrounding the rootlets, while the water is absorbed, and 
serves to nourish the plant. 
2. Sulphates of Lime, Alumina, &;c. 
Sulphate of lime occurs in the First Geological District only as an alluvion, inconsiderable 
in quantity, and resulting from the decomposition of pyrites in contact with materials containing 
calcareous matter, or as a deposit from mineral springs. 
In the Highlands, sulphate of lime is frequently seen incrusting hornblende and augitic 
rocks. One kind of hornblende rock is common, that is more or less distinguished by this 
mineral. It is formed by the decomposition of pyrites ; and the acid combining with the lime 
and crystallizing, causes the rock to crumble. These masses, when imperfectly crumbled, 
generally have a yellowish and reddish brown colour, from the oxide and red sulphate of iron, 
while the interior of the mass is filled with thin plates and crystals of the sulphate of lime. 
It is very common about West-Point. Acicular sulphate of lime, very beautiful, was found 
incrusting augite rocks which overlaid white limestone, at an old mine hole on Anthony’s Nose 
mountain, about three miles east of Fort Montgomery, near the top of the mountain. Mag¬ 
netic pyrites occur both in the augite and limestone. 
