[ i8a ] 
bis late Sydem of mineralogy, mentions a blue fub- 
dance, which feems to be of the fame kind, and 
which, I think, he fays, is found fomewhere in 
Pruflia. His account of it is very fhort; and I am not 
very certain with regard to it, as I have not the book 
by me. 
The place, where it is dug up, is of a marfihy na- 
ture, in the corner of an exhauded peat-mofs. Im- 
mediately under the fward lies a Jiratum , about a 
foot deep, of common peat ; next to that is the fub- 
ftance itfelf, with irregular Jlrice of a peaty matter all 
through it, to the depth of near another foot; and 
below this, I think, there is clay. While it is thus 
wet, and (hut out from the air, it is of a white co- 
lour, and feemingly of a fatty confidence, not unlike 
lime that has been prepared for cement. All the water 
in the neighbourhood of the place is in fome meafure 
impregnated with iron. When this fubdance is expofed 
to the air, it gradually as it dries afiumes the blue 
colour ; the peaty matter intermixed with it conti- 
nuing of the fame appearance as before. The whole 
mixed mafs is of a very friable texture, eafily crumb- 
ling betwixt the fingers ; and the blue part, gently 
rubbed between them, feels like a fine impalpable 
powder. It has hardly any fenfible fade ; what it has, 
approaches a little to that of fulphur : the fmell, when 
it is fird taken up, is fenfibly fulphureous, and if a 
piece of paper, with part of it adhering to it, be 
kindled, it fhews a dame fimilar to burning fulphur. 
The only means of feparating it from the black 
matter is by elutriation. When water is poured on 
it, and they are fhaken together, and then left at red 
for fome time, the black part fubfides to the bottom, 
2 and 
