ices are not particularly
new, consisting essentially of a combustible powder and chemical salts
which make the flame luminous and give it color when desired. Among the
ingredients are barium nitrate, potassium perchlorate, powdered
aluminum, powdered magnesium, potassium nitrate, and sulphur. One of the
simplest mixtures used by the English is,

Barium nitrate 37 per cent.
Powdered magnesium 34 per cent.
Potassium nitrate 29 per cent.

The magnesium is coated with hot wax or paraffin, which not only acts as
a binder for the mixture when it is pressed into its container but also
serves to prevent oxidation of the magnesium when the shells are stored.
The barium and potassium nitrates supply the oxygen to the magnesium,
which burns with a brilliant white flame. The potassium nitrate takes
fire more readily than the barium nitrate, but it is more expensive than
the latter.

Owing to the cost of magnesium, powdered aluminum has been used to some
extent as a substitute. Aluminum does not have the illuminating value of
magnesium and it is more difficult to ignite, but it is a good
substitute in case of necessity. An English mixture containing these
elements is,

Barium nitrate 58 per cent.
Magnesium 29 per cent.
Aluminum 13 per cent.

Mixtures which are slow to ignite must be supplemented by a primary
mixture which is readily ignited. For obtaining colored lights it is
only necessary to add chemicals which will give the desired color. The
mixtures can be proportioned by means of purely theoretical
considerations; that is, just enough oxygen can be present to burn the
fuel completely. However, usually more oxygen is supplied than called
for by theory.

The illuminating shell is perhaps the most useful of these devices to
the soldier. It has been constructed with and without parachutes, the
former providing an intense light for a brief period because it falls
rapidly. These shells of the larger calibers are equipped with
time-fuses and are generally rather elaborate in construction. The shell
is of steel, and has a time-fuse at the tip. This fuse ignites a
charge of black powder in the nose of the shell and this explosion
ejects the star-shell out of the rear of the steel casing. At the same
time the black powder ignites the priming mixture next to it, which in
turn ignites the slow-burning illuminating compound. The star-shell has
a large