kindled his camp fire by rubbing pieces of dry wood together until
they took fire, and this method is said to be used among some isolated
distant tribes at the present time. A later and easier way was to
strike flint and steel together and to catch the spark thus produced
on tinder or dry fungus. Within the memory of some persons now living,
the tinder box was a valuable asset to the home, particularly in the
pioneer regions of the West.

38. Safety Matches. Ordinary phosphorus, while excellent as a
fire-producing material, is dangerously poisonous, and those to whom
the dipping of wooden strips into phosphorus is a daily occupation
suffer with a terrible disease which usually attacks the teeth and
bones of the jaw. The teeth rot and fall out, abscesses form, and
bones and flesh begin to decay; the only way to prevent the spread of
the disease is to remove the affected bone, and in some instances it
has been necessary to remove the entire jaw. Then, too, matches made
of yellow or white phosphorus ignite easily, and, when rubbed against
any rough surface, are apt to take fire. Many destructive fires have
been started by the accidental friction of such matches against rough
surfaces.

For these reasons the introduction of the so-called safety match was
an important event. When common phosphorus, in the dangerous and
easily ignited form, is heated in a closed vessel to about 250° C., it
gradually changes to a harmless red mass. The red phosphorus is not
only harmless, but it is difficult to ignite, and, in order to be
ignited by friction, must be rubbed on a surface rich in oxygen. The
head of a safety match is coated with a mixture of glue and
oxygen-containing compounds; the surface on which the match is to be
rubbed is coated with a mixture of red phosphorus and glue, to which