414 
Schultzen suspects some error in those accounts which state their 
having been observed; and M. Walch, who entertains the same 
suspicions with Schultzen, accounts for the rarity of their being met 
with in lime-stone, or marble, to the calcareous mountains having 
been formed at the bottom of the sea, where vegetable matter would 
be least likely to accumulate ; but that they do occur in lime-stone 
strata is indubitable. 
The remains and the impression of leaves of trees are frequently 
found in the fissile calcareous stone of Oeningen, and in the calca- 
reous stones of other parts ; some of these may, perhaps, with pro- 
priety, be supposed to owe their present situation to the changes of 
very distant periods ; but others, especially those which are found in 
stones, apparently of a tufaceous origin, have been thus entombed 
in more modern times. Indeed it is rather to be expected, from the 
frequent falling of leaves on the soft margaceous, or tufaceous 
matter, on the borders of lakes and rivers, that instances of such 
preservations of their remains should be frequently met with ; which 
is the case in many places in Germany and Italy, as well as in 
several other parts of the world. 
Rounded nodules of argillaceous iron frequently contain in their 
centre the remains of plants, the forms of which are preserved in a 
state of wonderful perfection. The most particular account of these 
substances has been given by Dr. Woodward ; and, as it appears to 
have been the result of his own observations, I have here transcribed 
it. “ These nodules, with leaves in them, are called Cat-heads, and 
seem to consist of a sort of iron-stone, not unlike that which is found 
very plentifully at Robinhood’s-bay, in Yorkshire, and in the rocks 
near Whitehaven, in Cumberland ; where they call them Cat-scaups, 
and are frequently melted with the softer iron ores. These, perhaps, 
differ not much from those described by Dr. Lister, de Font. Med. 
by the name, as I remember, of Minerce Ferri Pilceformis, called 
Ball-mine in Staffordshire. These cat-heads are found only at Kenton, 
