L i8 7 ] 
colour depends, are iron and Tome vegetable aftrin- 
gent. Thefituation in which it is found favours this 
conjedure very drongly ; for, in the fird place, the 
water in the neighbourhood of it is all impregnated 
with iron ; and fecondly, in almod every peat-mofs, 
there are the remains of oak trees, dill freffi difperfed 
through them ; and both their wood and bark are of 
a drong aftringent nature. 
I do not pretend to fay, that thefe are its only in- 
gredients. I think we may conclude, from the light- 
nefs of the fubdance, that iron does not form a very 
great part of it j and the fmell, and the particular 
dame it exhibits in burning, would feem to diew the 
prefence of fulphur in it. This, however, can be 
only in a very fmall proportion, dnce fo much of it 
is foluble in acids, which do not at all affed fulphur. 
I fuppofe the praecipitate from acids condds chiedy of 
iron and earth. 
I have made fome trials on the blue powder after 
it was partly well freed from the black matter, in 
order to fee how far it might be ufeful as a paint : a 
quantity of it was rubbed in a glafs mortar with oil 
of walnuts ; but, after being thoroughly mixed with 
the oil, its colour was changed to black. It is probable, 
therefore, that little can be expeded from it as an oil 
colour ; but it retains its natural brightnefs when 
mixed with gum-water ; and, as it is naturally in a 
very fine powder, it is diffufed intimately through it 
without any difficulty, fo that, if it could be got in 
fufficient quantity, it would be a cheap and ufefuli 
water-colour. I think there isreafon to believe, that 
it might be found in mod peat-modes, as what feem 
to be the materials of which it is compofed are pre- 
Bb 2 fent 
