VOL. LI.] PHILOSOPHICAL TRANSACTiaNS. 313 



retort was thinly incrusted with something that resembled a saline concrete; but 

 was found to be only bituminous matter. In the bottom of the retort there re- 

 mained a very black gritty powder. Of this powder, one ounce was put into a 

 crucible, set in a melting furnace, and kept in a pretty strong fire for an hour. 

 The powder after it was cold appeared on the surface to be of a pale reddish 

 colour; but was not in the least altered underneath. It lost however in weight 

 near 3 drs. Some of the black powder taken out of the crucible, and thrown 

 upon a red-hot iron, burnt without flame; but emitted plentifully a heavy black 

 smoke. Two ounces of the black powder, which had been twice distilled, were 

 set on a clear fire in an iron ladle, and continually stirred from the time that the 

 ladle grew red-hot, and the matter began to emit a heavy black stinking smoke, 

 till no more smoke arose from it. The calcined matter remaining in the ladle 

 weighed 2 scruples, and seemed to be a kind of bole earth. This earth was eva- 

 porated in 2 ounces of rain water to one ounce, which some days after was 

 poured off clean from the sediment. This water had not the least saline taste, 

 nor did it give any sign of effervescence when spirit of nitre was dropped into it. 



From the preceding -experiments it appears that the substance called fossil- 

 wood consists, for the most part of water, and that a considerable quantity of 

 this principle is separated from it by a gentle heat; which seems to be the reason 

 why such fossil-wood, on being exposed to the sun and air, or kept in a dry 

 place, soon becomes full of superficial cracks, resembling a piece of timber, 

 which by lying long on the ground in the open air, has begun to decay: that 

 though the fossil-wood does not, like amber or pit-coal, yield by distillation a light 

 oil floating on its phlegm, and a volatile acid salt in a concrete form, yet that a 

 light oil and a volatile acid salt, in a considerable quantity, are intimately mixed 

 with the water which distils from it: that this fossil-wood diff^ers in several par- 

 ticulars from all wood belonging to the vegetable kingdom, which has been 

 examined by fire after the same manner. 



1st, Its powder burnt in a close vessel, and kept red-hot for a much longer 

 time than is sufficient to reduce the like quantity of vegetable charcoal, emits 

 (when sprinkled on a red-hot iron) a thick heavy black smoke. 2dly, The same 

 powder, burnt as before mentioned, does not easily take fire, nor burn of itself, 

 nor consume to ashes, even when exposed in an open crucible to a strong fire, 

 and kept in it ignited, and almost white for a considerable time. 3dly, The 

 matter left by this powder, after its phlogistic principle has been separated from 

 it by time and air, contains no alkaline salt, and appears to be an astringent 

 mineral earth ; whereas charcoal easily takes fire, burns freely without smoke, 

 and continues burning till it consumes to an ash; which consists of an alkaline 

 salt, and a pure earth fit for making cuppels, and by these marks is sufficiently 

 distinguished from all mineral substances. 



VOL. XI. 3 U 



