214 Mr. Stokes's Notice respecting apiece of F'ossil Wood. 



From Dr. Buckland, I have received some specimens of fossil wood from 

 Allesley, near Coventry, respecting which he has sent a communication to the 

 Society*, and at his request, the Rev. W. Bree has also sent to me specimens 

 from the same locality. Among these, which as far as I have been able to 

 ascertain, are all coniferous woods, are several in which some portions are in 

 a much better state of preservation than the rest of the specimens, although 

 the whole is now silicified. These cases are analogous to that from Antigua, 

 described in my former notice on this subject ; but in that instance, the longi- 

 tudinal section showed, that these better preserved portions were not more than 

 three-eighths of an inch in length, and these were the longest I had then ob- 

 served. In some of the AUesley specimens, these portions are full an inch in 

 length, and terminate in a fine point at each end, in the same remarkable 

 manner as I have above described to be the case, in the portion of the piece 

 of wood from the Roman aqueduct belonging to Mr. Brown. In others, the 

 best preserved portions are long narrow columns, going through the whole 

 length of specimens, three inches long, 



I have not much to offer in the way of remark, in addition to the simple 

 description of facts above stated. The instances in which some parts of 

 specimens of petrified wood, have the structure better preserved than the rest, 

 are not uncommon ; but in the detection of the commencement of a mineral 

 deposition in the vessels of the wood, and in Mr. Brown's remark of the me- 

 dullary rays remaining unchanged, while surrounded by the petrified longi- 

 tudinal fibres, we have, I believe, the first ocular demonstration of progressive 

 steps in the process of petrifaction. 



Since the above was written, Mr. Arthur Aikin has obligingly communicated 

 to me the following particulars of a piece of wood containing small particles of 

 metallic copper. 



" About twenty years or more ago, it was discovered that a bog near Dolgellau in Merioneth- 

 shire, contained small lumps of greenish blue carbonate of copper. It appeared to some speculators 

 in Liverpool, that a profit might be derived from cutting out the peat, burning it, and then smelting 

 the ashes, in which, of course, the copper would be containeJ. In prosecuting this undertaking 

 (which I believe was soon abandoned) small branches of oak and birch were met with, impregnated 

 more or less with metallic copper. Of these two or three small specimens came into my possession. 



" The copper probably came into the bog in the state of sulphate from the decomposition of 

 copper pyrites in the face of some adjacent rock, and was carried thence into the bog by the rain. 

 It must of necessity have entered the pores of the wood while in solution, and then have separated 

 itself from its oxygen and acid, but by what agency is not very clear to me. Both tan and Gallic 

 acid are very efficacious in reducing certain metallic oxids, and these two substances had probably 

 some share in producing the appearances in question." 



* Proceedings of Geological Society, No. 48, vol. ii. p. 439. 



