TAlffKING MATTER, kc* 95 



monly are present*; these facts, together with the sul- Ej.pej.;jneiits 

 phureous odour emitted by most of the mineral coals when &c. on an arti- 

 burned, appear strongly to evince the agency of the lat- ^^^^.^ substance 

 ter. Tjjat this has been the case, seems also to be cor- racters of tan- 

 roborated, by the great resemblance which (as has been ning nutter, 

 previously stated) the coals formed artificially from many 

 Tegetable substances bear to the mineral coals, especially 

 as the similarity is not confined to external characters, but 

 extends to other properties. 



By the action of sulphuric acid on yegetable bodies, a 

 much greater portion of their carbon is converted into 

 coal than when the same are subjected to the effects of fire. 



Several examples respecting the resins, have been men- 

 tioned in the seventh section of this Paper, and the result 

 of the experiment made upon oak perfectly accords with 

 them. 



Mr. Proust, in the course of some comparative expe- 

 riments on the proportions of charcoal afforded by diffe- 

 rent kinds of wood, obtained 20 per cent, from green 

 oak, and 1 9 per cent, from heart of oak +. 



But by sulphuric acid, from 480 grains of oak, I ob- 

 tahied 210 grains, or about 45 per ce«/. of coal, which 

 burned not like the charcoal obtained from the same 

 wood, but like many of the mineral coals ; and this was 

 also observed in the combustion of the greater part of the 

 coals obtained by the humid way from resinous substan- 

 ces. 



The experiment on oak also appears to refute another 

 objection to the vegetable origin of pit-co^l, namely, the 

 total absence of the alkalis, which on the contrary are so 

 constantly^ obtained from the ligneous parts of vegetables 

 by combustion J. But I have shewn, that when these bo- 

 dies are carbonized in the humid way either by muriatic 

 or by sulphuric acid, not any alkali can be obtained 

 from the ashes of coals so formed ; and this seems also to 

 be a farther proof, that the humid way has been employed 

 in the operations of nature to convert the above meution- 



-* Kirwan's Geological Essays, p. 324. 



f Journal de Physique, 1799, Tome 48, p. 469. 



i Ki rwan's Geological Essays, p. 350, 



ed 



