414 



having been observed ; and M. Walch, who entertains the same 

 suspicions with Schultzen, accounts for the rarity of their being 

 met with in iime-stone, or marble, to the calcareous mountains 

 having been formed at the bottom of the sea, where vegetable mat- 

 ter '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 FerriPilceformis, called 

 Ball-mine in Staffordshire. These cat-heads are found only at Ken- 

 ton, which is about two miles to the northward of Newcastle; and 



