.? 



>»estone t 



< 





e —)Ii 



*ton 



e, 



one. 



■vm 



°f quartz : 



From Carl 



<atk, Derbyl 

 one— Midt 



*> 



s, from Car 



one, show 



»us beds off 

 logical Sur 



mouth, 



•ocks whiel 



.. Quarry, 

 and- 



ir reton, lsl 



beds 



} 



= o 



;sil 



f/W 





s 



AND SILICIFIED WOOD. 



67 



occurring in seams and irregular masses, and patches in Upper 



-,-, 7 7 <-* ,-, ^ . - — Gaillky. 



Portland otone, 



36. 



Neictown Quarries, near Tisbury, Wilts. 

 Flint, from the ragstone beds of Lower Green- Sand: 



used for roads. 

 Kent. 



37.— Milky 



Q 



- 



quartz, with chlorite, from a greenstone 

 dyke traversing the slate quarries. — Llanberis, Caernar- 

 vonshire. 



Quartz of this nature has frequently been carried in 

 j Derbyshk solution in water, probably sometimes hot, and deposited 



in cracks along with other substances, some of which 

 now help to form metalliferous lodes. — A. C. XI. 



38. — Part of the silicified trunk of a coniferous 

 tree, probably allied to the pine ; from the " pine-raft " 

 ( Wealderi) which covers the shore between high and low 

 water marks, at Brook Point. — Brixton Bay, Isle of Wight. 



39. — Silicified fossil wood, from Gault. The bark 



pyritized. — Ridge, Wiltshire. 



40. — Part of the silicified trunk of a coniferous 



tree, from the " dirt beds " overlying Portland Sto?ie. — Isle 

 of Portland, Dorset. 



41. — Another specimen, from the Portland Stone Quarries 

 at Newtown, near Tisbury, Wilts. 



42. — Another specimen, partly converted into wood opal. 



Neictown, near Tisbury, Wilts. 



43, 44. — Another specimen, from the " submarine forest." 



West Lulworth, Dorset. 



45. — Silicified wood. 



The specimens Nos. 40 to 44 occur in strata, called by 

 the quarrymen the " dirt beds." These were the terrestrial 

 soils in which the trees grew. Sometimes their stools are 

 found erect, the roots spreading into the soils, and in other 

 cases the stems lie prostrate. They lie very near the base 

 of the Purbeck strata, a yellow limestone with cyprides 

 lying immediately below. The area in which they occur, 

 in Dorsetshire and Wilts, is comprised in maps 16. and 17, 

 and the position of the beds is shown in horizontal sections 



c 2 



