7 
periments, as feem to promife a full Dccifion in this 
Matten 
VI. Some Obfer^ations concerning the Snhjianu 
commonly called^ BlacJ^Leady ^he late 
Dr. Rob. Plat, F. K. S. 
THE Mineral Subftance, called, Black Lead (our^ 
common Lead being the true Black Lead, and (b 
called, in Oppofition to Tin, which is the White Lead) 
found only at Kefwick in Cumberland^ and there called* 
Wadt, or KeUow; by Dr. Merret^ Nigrica FaBrilisy from 
its ufe in Scoring, as the Ruhrica FairiliSy or the Red 
Mettal in it, that it has nothing of Fufiop, much lefs 
Dudility ; nor can it be reckoned amongft the Stones, 
for want of Hardnefi it remains therefore that it muft 
have Place amongft the Earths, tho^ itdiflolve not in 
Water, as moft Earths will, except ftiff Clays , and 
Ochres ; among the latter whereof I gueft it may be 
reckoned, it feeming ta be a fort of clofe Earth, of ve- 
ry fine and loofe Parts, fo burnt that it is become Black 
and Shining, difcolouring the Hands, as all the Ochres 
do ,• whence the moft Proper Name that can be given 
it, perhaps, may be Ochra Ifigra^ or Black Ochre, be» 
ing a Stony Sort, as there are Stony Sort of the Red: 
and Yellow Ochres, as well as Glay. 
Ochre is ; is certainly fo far from havin] 
thing of 
¥11. 
