44 



SKETCH OF THE 



of the varieties, if possible, to render my descriptions more intel- 

 ligible. 



No. 1 — May be considered as characteristic of this formation, and 

 specimens, exhibiting the appearances attempted to be represented, are 

 every where met with. On breaking a mass of this rock, we very gene- 

 rally observe that the surface presents the remains of what might have 

 been a succession of cylindrical-convex, — probably solid bodies,— one 

 fragment exhibiting these on a sort of baso-relievo, while the other pre- 

 sents corresponding hollows. These bodies taper to a point, and frequent- 

 ly occur minutely ramified at both extremities — this, at least, I have ob- 

 served in several instances. They are perfectly mineralised, are of the 

 same color as the mass, on which they appear generally as an incrust- 

 ation. In one or two instances, however, I have observed the terminations 

 of similar bodies on the mass itself, and in such cases they had obvi- 

 ously been arranged in bundles or fasciculi. In other instances, these 

 cylindrical bodies appear to send off, anastomosing branches which 

 unite them together. The latter may probably be a distinct variety. 

 All of the above have a perfectly stony aspect, and I could discover on 

 them nothing like a stellular structure, or any appearance of cells or 

 pores. The length of these cylindrical bodies varies from about a foot 

 to an inch or two inches — their breadth is also various, but they seldom 

 occur broader than in the instance represented. 



In one or two instances I have also observed longish tapering canals 

 in the masses of limestone, which had obviously been occupied by cylin- 

 drical bodies. These, at the time of deposition of this rock, had either 

 been detached from the bundles above alluded to, or had previously 

 existed in a separate state. The latter I think the most probable. Could 

 any of the above have formed the solid axis of any of the varieties of the 



