Illustration: SULPHURET OF LEAD.
Lead is a heavy metal, of a dull blueish tint, and very soft; it is
extensively used for covering roofs, for cisterns, and for pipes for
conveying water, as it is easily bent and joined, and is not acted
on by the water which passes through it. Lead melts at a heat below
that of redness, and, in combination with oxygen and carbonic acid,
forms the “white lead” of commerce so largely used as a paint. Oxide
of lead, called “litharge,” enters into the composition of flint
glass, and in combination with a larger quantity of oxygen forms “red
lead,” a substance much used in painting. Lead is found in many parts
of England, especially Cornwall, where many lead mines exist; it is
got from the sulphuret called “galena,” which is lead in union with
sulphur. What is called “black-lead” is not lead at all, but is an
ore of iron, being iron in combination with carbon. Lead is about
eleven-and-a-half times heavier than water.