ifling. But as the bore of his gun is hexagonal, the greater part of
the power employed to spin the shot tends directly to burst the gun.
Captain Scott, R.N., employs a solid projectile dressed to fit by
machinery; but the surfaces of the lands upon which the shot presses are
radial to the bore, so that the rotation of the shot tends, not to split
the gun, but simply to rotate it in the opposite direction.

_Mounting Heavy Ordnance_, so that it may be rapidly manoeuvred on
shipboard and protected from the enemy's shot, has been the subject of
so much ingenious experiment and invention, that in a brief paper it can
only be alluded to in connection with the following subject:--

THE STRUCTURE OF WAR-VESSELS.

_Size_. To attain high speed and carry heavy armor and armament,
war-vessels must be of large dimensions. By doubling all the lineal
dimensions of a vessel of given form, her capacity is increased eight
fold, that is to say, she can carry eight times as much weight of
engines, boilers, armor, and guns. Meanwhile her resistance is only
quadrupled; so that to propel each ton of her weight requires but half
the power necessary to propel each ton of the weight of a vessel of
half the dimensions. High speed is probably quite as important as
invulnerability. Light armor is a complete protection against the most
destructive shells, and the old wooden frigates could stand a
long battle with solid shot. But without superior speed, the most
invulnerable and heavily armed vessel could neither keep within
effective range of her enemy, nor run her down as a ram, nor retreat
when overpowered. And a very fast vessel can almost certainly run past
forts, as they are ordinarily situated, at some distance from the
channel, without being hit. Indeed, the difficulty of hitting a moving
object with heavy cannon is so great that slow wooden ships do not
hesitate to encounter forts and to reduce them, for a moving ship can be
so manoeuvred as to hit a stationary fort.

The disadvantages of large ships are, first, great draught. Although
draught need not be increased in the same degree as length, a stable
and seaworthy model cannot be very shallow or flat-bottomed. Hence the
harbors in which very large vessels can manoeuvre are few, and there
must be a light-draught class of vessels to encounter enemies of light
draught, although they cannot be expected to cope very successfully with
fast and heavy vessels. Second, a given sum expended