of the
essentials and soon disappear from the advertising world only to be
succeeded by others. The most common defect is lack of keeping
qualities. They will either absorb moisture or will evaporate; or
further chemical action will go on among the constituents, making them
dangerously sensitive or completely inert, or they will separate
mechanically according to their specific gravities.

For further clearness on the subject of the shell charges which have
so far been discussed, the following table is added of weight and
sizes of shells for United States naval guns, with their bursting
charges of powder:

6-inch com. cast steel shell 31/2 to 4 cal. long, wt. 100 lb., charge 6 lb.
8 " " " " " 250 " 141/2 lb.
10 " " " " " 500 " 27 "
12 " " " " " 850 " 45 "

ARMOR-PIERCING FORGED STEEL SHELL.

6-inch, 3 calibers long, weight 100 lb, charge 11/2 lb.
8 " " " 250 " 3 "
10 " " " 500 " 51/2 "
12 " " " 850 " 11 "

The chief efficiency of small quantities of high explosives having
reduced itself to the case of armor-piercing projectiles, it next
became evident that there was an entirely new field for high
explosives into which powder had entered but little, and this was the
introduction of huge torpedo shells, which did nor rely for their
efficiency upon the dispersion of the pieces of the shell, but upon
the devastating force of the bursting charge itself upon everything
within the radius of its explosive effect. It is in this field that we
may look for the most remarkable results, and it is here that the
absolute power of the explosive thrown is of the utmost importance,
provided that it can be safely used. Attention was at once turned in
Europe to the manufacture of large projectiles with great capacity for
bursting charges, and it has resulted in the production of a class of
shells 41/2 to 6 calibers long, with walls only 0.4 of an inch thick.
(If they are made thinner, they will swell and jam in the gun when
fired.)

These shells are used in long guns up to 6 and 81/2 inches caliber, and
in mortars up to 11.2 inches. They are made from disks of steel, 3 to
4 feet in diameter and 1 inch thick, and are forced into shape by
hydraulic presses. The base is usually sc