as the Krupp 6
inch and De Bange 6 and 8 inch, make a breach, the two former at a
falling angle of 22 deg., and the latter at one of 30 deg.. It is not easy to
lower the scarps enough to protect them from these blows, even by
narrowing the ditch in order to bring them near the covering mass of the
glacis.

The same guns are employed for dismounting the defender's pieces, which
he covers as much as possible behind the parapet. Heavy howitzers
destroy the _materiel_, while shrapnel, falling nearly vertically, and
bursting among the men, render all operations impossible upon an open
terre-plein.

[Illustration: FIG. 6.--STATE OF A CHILLED IRON CUPOLA BROKEN BY A 12
INCH BALL.]

The effect of 6 and 8 inch rifled mortars is remarkable. The Germans
have a 9 inch one that weighs 3,850 pounds, and the projectile of which
weighs 300. But French mortars in nowise cede to those of their
neighbors; Col. De Bange, for example, has constructed a 101/2 inch one of
wonderful power and accuracy.

Seeing the destructive power of these modern engines of war, it may well
be asked how many pieces the defense will be able to preserve intact for
the last period of a siege--for the very moment at which it has most
need of a few guns to hold the assailants in check and destroy the
assaulting columns. Engineers have proposed two methods of protecting
these few indispensable pieces. The first of these consists in placing
each gun under a masonry vault, which is covered with earth on all sides
except the one that contains the embrasure, this side being covered with
armor plate.

The second consists in placing one or two guns under a metallic cupola,
the embrasures in which are as small as possible. The cannon, in a
vertical aim, revolves around the center of an aperture which may be of
very small dimensions. As regards direct aim, the carriages are
absolutely fixed to the cupola, which itself revolves around a vertical
axis. These cupolas may be struck in three different ways: (1) at right
angles, by a direct shot, and consequently with a full charge--very
dangerous blows, that necessitate a great thickness of the armor plate;
(2) obliquely, when the projectile, if the normal component of its real
velocity is not sufficient to make it penetrate, will be deflected
without doing the plate much harm; and (3) by a vertical shot that may
strike the armor plate with great accuracy.

General Brialmont says that the metal of the cupola should be a