the characteristic Properties ofTamiin. 107 



peatedly washed, and was afterwards dried without heat. 

 T he sawdust then appeared, as I have observed, brownish- 

 black, and was pulverulent. It burned with some flainc, 

 emitted still a slight vegetal)le odour, and was re(Uieed to 

 ashes much sooner than the coal formed by sulpliuric acid, 

 but not so speedily as the oak charcoal. The ashes had an 

 ochraceous appearance, and were almost devoid oi any sa- 

 line substance, excepting a very slight trace of muriate of 

 potash. 



These two experiments therefore prove, 



1st, That W(X)d may bv sulphuric acid be converted into 

 a coal which in its properties is very ditVerent from charcoal, 

 although prepared from the san)e sort of wood ; and that the 

 coal thus formed by the action of sulphuric acid resembles 

 by its mode of burning, and by not affording any alkali 

 when reduced to ashes, those mineral coals which are devoid 

 of bitumen, 



2dly, That wood may also be converted into a sort of coal 

 by muriatic acid ; but in this case some of the vegetable cha- 

 racters remain, although, like tlie fonner, not any alkali can 

 be obtained from the ashes. 



§ VHI. 



Four different solutions have been proposed respecting 

 that difficult problem in the natural hislury of minerals, the 

 origin and formution of coal. 



The tirst is, that pit coal is an earth or stone chiefly of 

 the argillaceous genus, penetrated and impregnated with bi- 

 tumen. 



But ^^r. Kirwan very justly remarks, that the insuffi- 

 ciency of this solution is dcinonslratcd by Kilkeimy and 

 other coals which are devoid of bitumen, and also that the 

 quantity of earthy or stony matter in the most bituminous 

 coal.i bears no proportion to the weight of them*. 



The second and most prevailing opinion is, that mineral 

 coal is of vegetable origin ; that the vegetable bodies have, 

 subsequent to their being buried uniler vast strata of earth, 

 been luincralizcd by some unknown process, of which suJ- 



* Geological I'ssays, p. 31(;. 



phuric 



