Geological Society. 499 



A letter was, lastly, read from Robert Fitch, Esq., of Norwich, to 

 Edward Charlesworth, Esq., F.G.S., on the discovery of the Tooth of a 

 Mastodon in the crag at Thorpe, near Norwich. 



The pit in which the tooth was found is stated to present the fol- 

 lowing section : 



Top. Alluvium 5 feet 



Gravel 6 



Brick-earth, sand, and gravel 14 



Crag 5 



Large chalk flints, mixed with crag shells, 



principally Pectens 



Chalk 



It was in the bed of large chalk flints that Mr. Fitch found the 

 tooth ; and he adds that Thorpe adjoins the parish of Whitlingham, 

 in which Mr. William Smith discovered the tooth figured in his " Strata 

 Identified." 



June 8. — A paper was first read, entitled," Notice respecting a piece 

 of Wood partly petrified by Carbonate of Lime; with some remarks 

 on Fossil Woods, which it has suggested." Bv Charles Stokes, Esq., 

 F.G.S. 



Mr. Stokes lately received from Germany, with a collection of fossil 

 woods, a piece of recent wood, stated to have been found in an ancient 

 Roman aqueduct, in the principality of Lippe, in the Biickeberg, in 

 which some parts are petrified by carbonate of lime, while the remainder 

 of the wood, though in some degree decayed, is not at all mineralized. 

 This fact has afforded an explanation of the peculiarities of some other 

 instances of fossil wood, in which different parts of the specimen pre- 

 sent different appearances. Two other instances are particularly de- 

 scribed : one of silicified wood from Antigua, and one of a calcareous 

 petrifaction from Allen Bank in Berwickshire. In both these cases 

 it is inferred by the author, that the process of petrifaction com- 

 menced simultaneously at a number of separate points, and that it 

 was suspended when only parts of the wood had been petrified. The 

 unchanged parts would then be liable to decay; and in the specimen 

 from Antigua the process has been renewed after this remaining part 

 had decayed in a considerable degree, when that also became silici- 

 fied. In the calcareous petrifaction from Allen Bank (which is de- 

 scribed and figured by Mr. Witham, in his work on the structure 

 of fossil vegetables), the parts which had not been petrified al the time 

 the process was interrupted, have been entirely destroyed by the de- 

 cay which then ensued, and the intermediate spaces have been filled 

 up by tlie crystallization of carbonate of lime, without the removal of 

 the petrified portions from the positions in which they grew and in 

 which they had become mineralized. 



In the specimen from the Roman aqueduct the petrified portions 

 run in separate columns through the wood, as if conducted down- 

 wards by the vessels or woody fibres. In that from Allen Bank the 

 separate portions are spherical in form and independent of each other ; 

 and in that from Antigua they are independent, and though neailv 

 spherical not regularly so. Hence the author infers that a different 

 ex|)luriation must be sought for the manner in which the soliitioi; of 



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