: ON THE NEUTRAL, BLACK.
Earth Black, or Prussian Black, is a native earth, combined with iron
and alluvial clay. It is found in most countries, and should be washed
and exposed to the atmosphere before being employed. Sea-coal, and
other black mineral substances, have been and may be used as substitutes
for the more perfect blacks, when the latter are not procurable, which
now seldom or never happens.