476 Geological Society. 



A description was then given of the mineralized condition of the wood , 

 and its organic structure. On the surface of many of the specimens 

 from the gravel, is a multitude of small spherical cavities, each of which 

 was once filled with a minute round concretion of oxide of iron or im- 

 perfect jasper j and innumerable specks formed by these concretions 

 pervading the interior of the specimens, appear to have been formed 

 in a manner analogous to that which produced the eye agates in the An- 

 tigua wood. The tree in Mr. Gibson's garden, and many of the larger 

 fragments found in the gravel, abound with minute longitudinal 

 apertures resembling those in shrunk and shaken timber; many of 

 these are filled with red oxide of iron, or lined with beautiful crystals 

 of dark-coloured quartz. In two specimens Dr. BuckUmd noticed lon- 

 gitudinal holes about ^th of an inch in diameter, which had apparent- 

 ly been perforated by the larvae of some insect. In the large collection 

 formed by Mr. Bree, the author sought in vain for examples of the 

 petrified palms, psarohtes and helmintolites described by Cotta and 

 Sprengel as found in Saxony, in beds considered to be the equivalents 

 of the new red sandstone of England j all the Allesley specimens are 

 either referrible to decided coniferae, which have distinct concentric 

 lines of growth, or exhibit a compact structure in which neither large 

 vascular tubes nor concentric lines of growth are visible. 



A paper entitled ** Further notice on a partially petrified piece of 

 wood from an ancient Roman aqueduct at Eilsen, in the Principality 

 of Lippe-Biickeberg," by Charles Stokes, Esq., F.G.S., was next 

 read. 



Since his former communication on this subject, (Lond. and Edinb. 

 Phil. Mag. vol. ix. p. 499) the author has been shown by Mr. Robert 

 Brown a specimen from the same partially petrified piece of wood ; 

 and Mr. Brown has pointed out to him, in its longitudinal section, 

 that the petrified portions are spindle-shaped bodies, about two inches 

 in length, in some instances completely inclosed within and sur- 

 rounded by the unchanged wood, and are not, tlierefore, as formerly 

 conjectured by the author, connected by such an external supply of 

 carbonate of lime to particular points as might have been derived from 

 stalactites formed in the building. 



Tne author also stated that Mr. Brown had called his attention to 

 the remarkable circumstance exhibited in this specimen, that though 

 the change in the longitudinal fibres appears to be complete, yet the 

 medullary rays are still in their ligneous state ; and on referring to 

 the specimen formeily described, Mr. Stokes has found some instances 

 in which a part of the medullary ray which passes through the petri- 

 fied portion has not been so completely changed as the surrounding 

 longitudinal fibres, or the part of the same ray which is more in the 

 centre of the petrified portion. 



Of the unpetrified part of the specimen, some portions are much de- 

 cayed and worm-eaten, while others are hard and apparently in good 

 preservation; the line of separation between the two conditions being 

 occasionally remarkably well defined. On submitting portions of 

 each to the action of muriatic acid, Mr. Stokes found that the decayed 

 part exhibited only a slight effervescence, while that which appeared 

 in good preservation gave oflf a much greater quantity of gas, and 



