Natural History. -^Mineralogy. S9l 
riate of barytes, and nitrate of silver, produced copious brown 
precipitates, as did also protonitrate of mercury and nitrate of 
lead.' But oxymuriate of mercury produced an immediate pre- 
cipitate, and that obtained from acetate of zinc was of a paler 
brown colour.” From these experiments. Dr Prout considers 
the black principle obtained from the urine by the action of di- 
lute acids, as a new body, possessed of acid properties ; and, if 
this is confirmed by farther observations, be proposes to call it 
Melanie Acid. 
181 Conversion of Iron into Plumhago . — The following interest- 
ing fact has been pointed out to us by a correspondent, in Beck- 
mann’s History of Inventions.^ vol. iv. p. 243. — Those who 
consider steel only as the most perfect kind of iron, may per- 
haps think with Plutarch, that the softer and more equable part 
of the metal is first converted into rust, and that the better part 
of the whole mass is thus separated from the rest. Without en- 
tering on a farther discussion of the subject, I shall only men- 
tion an observation made a few years ago. In digging up the 
floor of a cellar in an old house near Gottingen, there was found 
an anvil which had lain under the damp earth for many years. 
It still retained its original form and size, but was become so 
soft that it could be easily crumbled to pieces. When broken,, 
there were seen, every where on the fracture, exceedingly white 
grains, with a metallic brightness which resembled polished steely 
and were attracted by the magnet ; consequently, had not yet 
been converted into rust.” 
nr. NATURAL HISTORY. 
MINERALOGY. 
19 . 'The Secondary or Flcetz Formations^ as determined hy Wer- 
ner^ the same in Great Britain^ as in Germany. — Mr Weaver, 
a pupil of Werner, in his valuable view of the floetz rocks in the 
Annals of Philosophy, concludes his details with the following 
remarks : 
It follows, from the whole of these premises, that the floetz 
formations of Werner strictly commence with the old red sand- 
stone of England, and not, as has been stated, with the new or 
calcareous conglomerate. It follows, also, that the charge of 
c c 2 
