ROOM I. FOSSIL WOOD OF AUSTRALIA. 59 



were obtained, appear to occur under similar conditions, and 

 to have been subjected to the same changes, as those of the 

 Isle of Portland above described. They are found with the 

 trunks erect, to the height of a few feet, in a bed of arid sand, 

 apparently on the spots where they grew ; the branches and 

 upper part of the stems being scattered around. They so 

 entirely preserve their natural ligneous appearance, that an 

 agricultural colonist mentioned as among the extraordinary 

 sights he witnessed on his first arrival in New Holland, the 

 burning of trees into excellent lime to manure the ground. 



A forest of these silicified trees occurs on the eastern coast 

 of Australia under the following circumstances. At the 

 base of a mountain range composed of conglomerates and 

 sandstones, with subordinate beds of lignite, terminating on 

 one side of Lake Macquarrie, an alluvial flat extends to the 

 water's edge, covering the sandstone rock, which lies in situ 

 beneath. Over this plain stumps of petrified trees project 

 a few feet above the soil, presenting the appearance of a forest 

 in which the trees are all cut or broken off at the same level. 

 At the distance of a few yards from the shore, a reef is 

 formed by vertical rows of stems, which project above the 

 water. Many of the fossil trees on the shore have the remains 

 of roots extending into the sandstone below the alluvial 

 deposit ; and, like those in the Isle of Portland, are in some 

 instances surrounded by an accumulation of stone that forms 

 a mound of a higher level than the surface of the ground. 

 These trees are of a large size ; often six feet in diameter. 

 The concentric annular rings, and the medullary rays and the 

 coniferous ducts, are beautifully preserved in silex and chalce- 

 dony ; in several examples, from 60 to 120 annual circles of 

 growth were observable. 



In the valley of the Derwent in Van Diemen's Land, opal- 

 ized coniferous trees of a similar character were observed 

 under conditions yet more extraordinary, by the distin- 

 guished philosophical traveller, Count Strzelecki. Truncated 

 stems of trees are standing erect in a bed of porous and 

 scoriaceous basalt, and trachytic conglomerate : but in some 

 instances these are only casts of trunks that were consumed 

 by the melted basalt when first ejected. This curious pheno- 

 menon can only be explained by supposing that the silicified 

 stems were able to resist the intensity of heat of the incan- 



