8 E. A. Neicell Arher — On a large Siliclfied Tree, 



specimen and tlie crowded nature of the Natural History exhibits, 

 then at Bloomsbury, it was not possible to exhibit it until their 

 removal to the more suitable and spacious quarters at South 

 Kensington had been completed. 



From the geological standpoint, this tree is especially interesting 

 in the manner of its occurrence. The Basalts of the Macquarie 

 Plains are of Tertiary age, but thei'e seems to be some difference of 

 opinion as to whether they belong to the earlier^ or later- period. 

 McLachlan's ^ description of this specimen states that the tree •' was 

 imbedded in lava, and distinctlj^ surrounded by two flows of scoria." 



The association of plant remains with volcanic outpourings, 

 especially with the more basic tuffs and lavas, is by no means of 

 rare occurrence. Excellent illustrations may be found in the rocks 

 of this countr3\ In the Tertiary leaf-beds of Mull,"* well-preserved 

 impressions of leaves, similar to Platanus and other recent genera, 

 occur in gravels closely associated with sheets of basaltic lava. 

 Calcified stems and other fragments of plants of the greatest botanical 

 importance have been discovered in beds of volcanic ash in the 

 Lower Carboniferous rocks of Petticur, near Burntisland, and at 

 Laggan Bay in the island of Arran.'' Silicified stems in association 

 with basalts and other igneous rocks are known from many parts 

 of the world, especially from South America, where their occurrence 

 has been described by Darwin." 



The vertical position in which the tree was found is emphasized 

 by Hooker and by McLachlan. It would be of some interest to know 

 whether this trunk once formed part of a forest which, at some 

 period or other, was overwhelmed by showers of ashes and lava-flows. 

 On this point there is, however, little information. McLachlan 

 suggests that the vertical position is more or less accidental, and 

 states that the base of the tree was embedded in sand. 



The tree, as it stands now, is decorticated, only the woody tissues 

 being seen. The outer portion is opalized and fairly hard, but the 

 more internal tissues crumble away to a fine white powder at the 

 slightest touch. This powder consists of the isolated woody fibres 

 of the stem. Sir Joseph Hooker has so gi'aphically described the 

 condition and structure of the specimen that I cannot do better than 

 quote his remarks.' " The bark (?) is of a different colour and more 

 consolidated than the interior, resembling the most beautiful agate. 

 The woody part reminded me of the lignite, so common in Lough 



Neagh, in the north of Ireland The most remarkable 



circumstance, however, connected with this fossilized tree, is the 

 manner in which the outer layers of wood, when exposed by the 



1 Johnston: " Geology of Tasmania," 1888, pp. 215 (table) and 294. 



'^ Stephens : Papers and Proc. Roy. Soc. Tasmania for 1897, p. 54 (1898). 



^ See note 4, previous page. 



* Starkie Gardner: Q.J.G.S., vol. xliii (1887), p. 270. 



5 Wiinsch, Trans. Geol. Soc. Glasgow, vol. ii (1865), p. 97; and Brvce, "The 

 Geology of Arran," 4th ed. (1872), p.' 123. 



* Darwin: "Geological Observations," 2nd ed. (1876), p. 394, etc. 

 ' Hooker: ibid., p. 25. 



