322 
GEOLOGY OF THE FIRST DISTRICT. 
Limestone containing carbonate of iron is common, and in its unchanged state it does not 
show its fossils distinctly, but by weathering loses its carbonate of lime, and leaves a yellowish 
mass of spongy impure limonite, filled with the impressions of shells. Loose blocks of this 
rock were seen in abundance one mile north of Jefferson Academy, Schoharie county. Fu- 
coids and the same terrene plants * were observed here, as on the descent of the mountain 
north of Summit.f 
The grey grits by the falls at the tannery, at North-Blenheim, contain fossil shells. They 
* Some of the plants referred to are figured in Prof. Vanuxera’s Report, pp. 157,161. 
Fig. 15. 
t The various fossils of the different divisions will be figured, named and describe 1 in the palmontological part of this work. 
