Miscellaneous, 237 



four degrees, Riid often furnished with large cicatrices of branches ; tliey 

 nro conseijuently only friiu;Mionts, scattered about in those localities 

 during the cultivation of the forests aiul fields, of stt-nis which very 

 j)robably occur in the interior of the sandstone rock, from which they 

 only project singly. Smaller stems or branches, of less than one 

 foot in thickness, arc wanting ; and it is remarkable that I have never 

 found any such in the cari)onifcrous formation, whilst in the petrified 

 forests of the tertiary fornuUiou, for example, in Kgypt and Java, these 

 are even more abundant than the larger ones. They all belong to 

 coniferous plants, similar to the Araucarice; one of them decidedly 

 is a new species, Aruucaritcs Sc/trol/ianiis (named in honour of 

 M. B. Schroll), and the other is A. lirandliiicju, which has been 

 found in the carboniferous strata of England*, Saarbriicken, Bohemia, 

 and Silesia. I obtained a specimen of the former species, six feet in 

 length and three feet in thickness, from M. Schroll ; it is now an 

 ornament of the Palaeontological portion of the Botanic Garden at 

 Breslau. 



As regards the process of petrifaction itself, the previous experi- 

 ments and observations mentioned by the author in the years 183G 

 and 1837, at the meetings of German Naturalists at Jena and Prague, 

 and in the 'Fossil Flora of Silesia,' published in 1811, were, at the 

 reading of this paper before the Silesian Society, Nov. 27, 18.07, 

 brought together with his more recent ones, and illustrated bv the 

 exhibition of specimens. The former started from woods discovered 

 in the existing world, j)etrlfied by carbonate of lime or oxide of iron, 

 to which native copper has very recently been added as a petrifying 

 medium, as this has filled up cells and vessels in a fragment of beech- 

 wood communicated to me by my honoured friend Ilaidinger. The 

 examination of fossil woods shows, that after they are filled up by 

 the various petrifactive media (carbonate of lime, silica, the various 

 forms of oxides of iron and copper, cinnabar, baryta, gypsum, lead- 

 glance and clay), in by far the greater number of cases, notwith- 

 standing the solid, perfectly mineralized appearance of the exterior, 

 a larger or smaller quantity of cells and vessels are still present, which, 

 probably in consequence of the long duration of the process, have 

 become changed into brown-coal, although retaining the cellulose 

 here and there ; hence the prevailing brown colour of petrified woods, 

 which, however, are still frequently tinged in various ways by oxide 

 of iron. Other differences, which can only be hinted at here, may 

 be explained by the state in which they were at the time of fossili- 

 zation. "We need only refer to the infinitely variable texture of the 

 woody plants of an existing forest. A complete disj)lacemeut of the 

 organic j)arts very rarely takes place, as perhaps in the so-called 

 pyritized woods, and woods mineralized by brown iron-stone, as also 

 in the crystalline wood-opals of Hungary, Bohemia, the Rhine di- 

 stricts, &c., and there in consequence of a process of decomj)osition 

 of the organic matter. In the latter, cells still occupied by air- 

 bubbles are often found. 



In conclusion, the process of solution of the petrifactive minerals 



[* Dadoxylon Brandlingi of Morris's * Catalogue of British Fossils.' — Ed.] 



