23 



It is found in many parts of the world ; but some of 

 the finest specimens are obtained in the neighbourhood of 

 Schemnitz and at Telkabanya in Hungary. 



It is frequently found in this island in the diluvian 

 detritus, and in almost the whole of the green sand form- 

 ation. Very large fragments are found in the Portland 

 stones, the interstices of which are often beautifully 

 sprinkled with quartz crystals. Interesting specimens are 

 also discovered in the gritstone of the same formation, in 

 the Blackdown-pits of Devonshire, and are frequently ren- 

 dered very interesting by the delicate amianthine form in 

 which the silex is disposed. Specimens are also found in 

 the sands of Bedfordshire. It is but rarely found in chalk ; 

 it however forms the nucleus of a flint nodule which is said 

 to have been obtained in Berkshire. 



Besides the general characters of siliceous wood, the 

 peculiar resinous glistening lustre which it often possesses 

 demands particular notice. It exists in so many degrees, 

 and under such distinct modifications, as to divide it into 

 several species. This peculiar lustre, so nearly resembling 

 that of wax or rather of resin, giving such an appearance as 

 might be expected from a mixture of fluid silex and bi- 

 tumen, and existing in specimens in which strong and 

 indisputable markings of the woody fibre were to be seen, 

 gave rise to the opinion offered in a former work, that these 

 specimens were the result of the siliceous impregnation of 

 wood in different degrees of bituminization ; the gently 

 contorted and softened lines of the ligneous texture pre- 

 senting the appearance of their having been in a softened 

 state previous to their petrifaction. 



With the hope of determining whether bituminous or 

 even carbonaceous matter existed in these specimens or 

 not, several experiments have been employed; but when 

 the fugacious nature of bitumen and the refractory nature 

 of silex, yielding only to the most destructive processes, are 



