100 Experiments on a Substance which possesses 



imperfect carbonization of the original vegetable substances. 

 Whether this has been the case, or whether the tannin has 

 at times been afforded by heath and other vegetables growing 

 upon or near the peat, still appears to me to be uncertain ; 

 but, whatever may be the origin, I have never yet been able 

 to detect any tanning substance in peat, although I have 

 examined a considerable number of varieties, some from 

 Berkshire, and many from Lancashire, which were obli- 

 gingly sent to me for this purpose by my friend John 

 Walker, esq. F.R.S. Mr. Jameson has also made the same 

 observation *, so that there cannot be any doubt (whatever 

 the origin of the tanning matter may have been) that it has 

 speedily been extracted and drained from the substances 

 which at first contained it. 



This effect is a natural consequence of the great facility 

 with which tannin is dissolved by water, and extends even 

 to the most solid vetretable bodies : I shall here jrive an ex- 

 ample. 



In the Philosophical Transactions for 1799) Dr. Correa 

 do Serra has given an account of the submarine forest at 

 Sutton, on'the coast of Lincolnshire, where submerged ve- 

 getables are found in great abundance, including trees of 

 different descriptions, especially birch, fir, and oak. At the 

 time when I was engaged in those experiments on the Bovey 

 coal, and other substances of a similar nature, which have 

 been printed in the Philosophical Transactions for 1804, 

 Sir Joseph Banks had the goodness to send me a piece of 

 the oak, which was perfect in all of its vegetable characters, 

 and did not appear to have suffered any change, excepting 

 that it was harder, and of a darker colour, than recent oak 

 wood. From some experiments which I then made, I found 

 that after incineration it afforded potash, similar to the re- 

 cent wood, and contrary to substances like the Bovey coal, 

 which retain the vegetable external characters, although im- 

 perfectly converted into coal f. 



In the course of my experiments on tannin I reduced 



* An Outline of the Mineralogj' of the Shetland Islands, &c. 8vo edition, 

 p. 174. 

 t Phil. Trans, for 1804, p. 290. 



about 



