96 rANNINO MATTER, &C. 



Experiments, ed substances into pit-coal ; for supposing fire to have 

 fidalsubstance ^^^^ the agent, it does not appear easy to conceive how 

 having the ch..- the alkali could have been destroyed or separated*. 

 ractcrs of t.m- Kvery circumstance seems therefore to support the 

 opinion of those who consider the pit-coals as having been 

 formed in the humid way, principally from vegetable bo- 

 dies, and most probably by the agency of sulphuric acid ; 

 and allowing that animal substances may also have con- 

 tributed to the production of coal, yet this would not 

 militate against the above mentioned opinion, as the effects 

 produced upon them by that acid would in all the essen- 

 tial points be perfectly similar +. 



An 



* Some have attempted to account for the absence of alkali in the 

 ' Bovtry coal and common pit-coal, by supposing that the vegetable 



bodies (from which these have been formed) were previously de- 

 prived of alkali by simple lixiviation during their immersion in wa- 

 ter. But in page 127 of this Paper, I have shewn that the submerged 

 oak of Sutton, although deprived of its tannin, still retained its pot- 

 ash, which certainly would not have been the case if the latter like 

 the former could have been separated from the wood by mere solu-^ 

 tion. When wood is reduced to ashes, the alkali becomes complete- 

 ly denuded by the destruction of the woody fibre, and consequently 

 jnny be immediately taken up by water ; but when wood is convert- 

 ed into coal in the humid way by means of an acid, then it seems to 

 me that two effects take place ; for the intimate combination of the 

 alkali with the woody fibre becomes in a great measure destroyed by 

 the carbonijiation of the latter, whilst a simultaneous action arises 

 in the affinity between the aci^d and the alkali ; so that if coal has 

 been formed by suih means, the alkali must have been separated from 

 the wood, in the state of a dissolved neutral salt. 



f From the nature of the experiments which have been related in 

 this Paper, I have nnavoHably been induced to notice concisely the 

 different opinions on the formation of coal by the humid way ; but 

 ' I did not intend to have mentioned any of those which have been 



brought forward in favour of the immediate or indirect action of 

 fire, as I only wished to express my sentiments respecting the most 

 probable of the former opinions. 



Since however this Paper was written and partly read before the 

 Royal Society, I have been favoured by Sir James Hall, with a 

 copy of his Paper, intitled " Account of a Series of Experiments iheiving 

 " the Effects of Compression in modifying the Action of Heat ;" and I am 

 fully of opinion that the scientific world has not for a long time 

 received any communication of more importance, or in which more 

 accuracy, ability, and perseverence have been displayed. The 

 effects which Sir James Hall has produced on carbonate of lime, 

 by heat acting under compression, certainly removes a great and at 



one 



