C *«♦ 1 
XVHt. Softie Experiments upon the Ochl’a friabilis nigra 
fufca oj Da Cofta, FoJJ. p, 102.; and called by the 
Miners oj Derby (hire, Black Wadd. By Jofiah Wedgwood* 
F. R. S. 
Read March t 3, 1 783. 
T HE extraordinary circumftance of this fubftance taking 
fire upon being (lightly mixed with linfeed oil, firft 
difcovered by accident in the year 1752, at Mr. bAssano’s, a 
painter in Derby, has rendered it a fubjeft of curiofity ; but* 
as it is now employed in coniiderable quantities, and very ad- 
vantageoufly, as an oil-colour ill fhip and houfe-painting, it 
has a better claim to our attention ; and it is hoped, an attempt 
towards the further inveftigation of fo curious and ufeful ail 
earth may be acceptable to this illuftrious Society. 
It is many years fince I firft collected fome of this earth, 
which bafletted out in a hollow way near Winfter, in Derby- 
fhire, and tried fome experiments upon it ; but as they were 
not very interefting to me at that time, and my hands being 
full of other matters, I made no further ufe of it till December 
laft, when a feries of experiments being made at the Piefident’s 
houfe upon its inflammable property when mixed with oil, at 
which john walsh, Efq. and l'everal other gentlemen were 
prefent, Mr. walsii was kind enough to fend me a fpecimen 
from thence, and exprefs his defire that I would analvfe, and 
make fome further experiments upon, this extraordinary fub- 
fiance. 
* Mr. 
