41 o Doubts rcfpeBiiig the SyJwy Enrlh, 



tlic refuli W.15 a blickifli bead like the former, only fmooth on the outdde, with fomcthing 

 of meiallic brightncfs, not unlike that of black-kail. Both beads were very light, and had 

 q confideiable cavity within. All the internal part was whitilh, without the lead metallic 

 afpecl j and the external glorty blacknefs appeared to be only the ftaiu which charcoal 

 powder communicates in flrong fire to fome earthy bodies that have a tendency to vitijfy. 

 By boiling in concentrated marine acid, a part of the beads was diflblved, precipitable, as at 

 firft, by water ; but an accident prevented the procefs from being continued fufficiently to 

 determine whether the whole could be diflblved or not. 



By this fufibility in the fire, folubility in one only of the common mineral acids, and parting 

 with the acid in a heat below ignition, precipitability by water, and non-prccipitability byPruf- 

 fian lixivium, this fubftancc is llrongly difcriminated from all the known earths und metallic 

 calces. And as it fuffers no decompofition from any of the alkalis in any of the ufual modes 

 of application, I prcfume it cannot be confidcicd as a combination of any of thofe earths or 

 calces with any of the known acids ; for all the combinations of this kind would, in one or 

 other of the above methods of trial, have had the earth or metal difcngaged from the acid. 



Whether this fubftance belongs to the earthy or metallic clafs, 1 cannot abfolutely deter- 

 mine ; but am inclined to refer it to the earthy, becaufe, though brought into perfeiSk fufion 

 in contaft with inilammable matter and in clofe vcffels, it does not aflume tlie appearance 

 which metallic bodies do in that circumllance *. 



The black fubdance, which feems to have compofed about one-fifth part of the crude 

 mineral, was found to refemble plumbago in its leading properties, but its rcfidue did not 

 appear to be iron. The remaining three-fifths of the mineral, which refilled the humid at- 

 tacks in Mr. Wedgwood's experiments, was probably filex ; but he does not fpeak of any 

 dire£l examination of its properties by fufion with alkahs, the fparry acid, or otherwife. 



On the preceding experiments of M. KlaprotK and the late Mr. Wedgwood, the quef- 

 tion which in the firft place appears to demand folution, is, whether the fame mineral was 

 examined by both chemifts .' If this fliould not appear probable, it will be unneceflary to 

 enter upon tlie fubfequent enquiry, which fet of experiments is moft likely to be erroneous? 



On the hiftorical evidence, as far as regards the famencfs of the parcels of mineral, I think 

 there is little to be faid. Both were obtained from Sir Jofeph Banks; the firft direclly, and the 

 latter with the intervention of the refpciflable, and as it may be conclude<l careful, M. Haidin- 

 ger. Neverthclefs, if the obvious defcription and decided experiments Ihould point out a 

 difference, it will afford more than a prefumptive proof that they were not the fame. 



1. M. Klaproth's mineral wasgreyilh, and bec.ime blueifti by levigation. iMr. Wedgwood's 

 was a fine white Hind, a foft white earth, with fome colourlefs micaceous particles, and a 

 few refembling plumbago. When levigated, it became black, (hining, foft, and unfluous. 



2. Klaproth's marine folution, after filtration, afforded no precipitate by the addition of 

 water. Wedgwood's folution in the fame acid, when cold, fettled fine ; and, decanted off 

 clear, afforded a white precipitate with water to the whole amount of its contents. After 

 fix meafurcs of water had caufed much of the precipitate to fall, the liquor was filtered, 



' Here ends the citrafl in Mr, Wedg-vooJ s own wonls. 



and 



