78 Flint Ridge Section. 
ganic remains of what appear to me to be Ventricolites, bearing a 
strong resemblance to those described by Dr. Mantell, in the flint 
or chalk Zoopbytes of the south of England.—10 feet. 
5. Resting on the calcareous rock, reposes the great siliceous de- 
posit. At this place the upper part of the bed is very white and 
compact, containing however, many small Encrini. Below, it is of 
various hues, strangely diversified from a deep indigo, to green, yel- 
low, red, horn color, &c. Near the superior portion of the bed it is 
more porous, contains a little lime and looks as if it had been tra- 
versed in all directions, by small worms, leaving brown colored pas- 
sages of the size of acommon pin. ‘This is the portion chosen for 
the construction of mill stones ; and when properly selected, affords 
an excellent instrument for the manufacture of flour. I received this 
summer, a specimen of cellular quartz, from the shore of the Missis- 
sippi, in Calhoun county, Illinois, containing a large and very fine 
Spirifer cameratus, similar to those found here ; proving the habitat 
of this shell to have been widely extended over the bed of this an- 
cient ocean.—7 feet. 
6. Resting on the uper surface of the main siliceous rock, is a de- 
posit of a much more loosely cohering calcareo-siliceous material, 
containing considerable iron, and resembling bog ore, being probably 
the remains of the mineral matter held in solution by the warm water 
of the ocean, after the more siliceous portion had been thrown down. 
‘That this was actually the fact, is more than probable from the ir- 
regular and diffuse manner in which this deposit rests on the other 
strata, being confined to a narrow belt of only a few miles in width ; 
it must have been discharged from the bowels of the earth through a 
fissure in the bottom of the ocean, opened by the force of internal 
heat, and the expansive power of confined gases, and gradually pre- 
cipitated in the vicinity of the opening, which on more minute exam- 
ations, I doubt not may be accurately traced.—2 feet. 
7. Above this is a deposit of rich yellowish, argillaceous soil, once 
covered with a heavy growth of forest trees, but now under cultiva- 
tion. The siliceous rocks abound in fossil shells, affording presump- 
tive evidence of the assumed fact, that they lived and propagated in 
the bed of the ocean for many years after the precipitation of the 
siliceous mud; and that they finally perished and became silicified 
after and during the period of the change from water to dry land. , 
The genera and species are, many of them, similar to those found in 
the upper calcareous rocks at Zanesville ; and figured and described 
