IV] CASTS OF TREES. 71 



perfection'. Dr Thomas in an account of the amber beds of 

 East Prussia in 1848, refers to the occurrence of large fossil 

 trees ; he writes : 



" The continuous changes to which the coast is exposed, often bring to 

 light enormous trunks of trees, which the common people had long 

 regarded as the trunks of the amber tree, before the learned declared that 

 they were the stems of palm trees, and in consequence determined the 

 position of Paradise to be on the coast of East Prussia 2." 



In 1887 an enormous fossil plant was discovered in a 

 sandstone quarry at Clayton near Bradford^ The fossil was 

 in the form of a sandstone cast of a large and repeatedly 

 branched Stigmaria, and it is now in the Owens College Museum, 

 where it was placed through the instrumentality of Prof 

 Williamson. The plant was found spread out in its natural 

 position on the surface of an arenaceous shale, and overlain by 

 a bed of hard sandstone identical with the material of which 

 the cast is composed. Williamson has thus described the 

 manner of formation of the fossil : 



"It is obvious that the entire base of the tree became encased in a 

 plastic material, which was firmly moulded upon these roots whilst the 

 latter retained their organisation sufficiently unaltered to enable them to 

 resist all superincumbent pressure. This external mould then hardened 

 firmly, and as the organic materials decayed they were floated out by 

 water which entered the branching cavity ; at a still later period the same 

 water was instrumental in replacing the carbonaceous elements by the 

 sand of which the entire structure now consists*." 



Although the branches have not been preserved for their 

 whole length, they extend a distance of 29 feet 6 inches from 

 right to left, and 28 feet in the opposite direction. 



The fossil represented in fig. 1 (p. 10), from the collection of 

 Dr John Woodward, affords a good example of a well-defined 

 impression. The surface of the specimen, of which a cast is 

 represented in fig. 1, shows very clearly the characteristic 



1 For figures of fossil plants in amber, vide Goppert and Berendt (45), 

 Conwentz (90), Conwentz (96) &o. 



2 Thomas (48). ' Adamson (88). 



- Williamson (87) PI. xv. p. 4S. A very fine specimen, similar to that in the 

 Manchester Museum, has recently been added to the School of Mines Museum 

 in Berlin; Potonife (90). 



