called
tinclads, but officially light-draughts, were river stern-wheel
steamers purchased for the service after the suggestion of
Flag-Officer Davis, and covered all round to a height of eleven feet
with iron from half to three-quarters of an inch thick, which made
them proof against musketry. The protection around the boilers was
increased to resist the light projectiles of field artillery. They
quartered their crew comfortably, and could on a pinch, for an
expedition, carry 200 men. The usual battery for these vessels was six
or eight 24-pound brass howitzers, four on each side, with sometimes
two light rifled guns in the bows. This armament was of little use
against works of any strength, but with canister or shrapnel could
keep off the riflemen, and meet on equal terms the field artillery
brought against them on the banks of the narrow streams, often
thickly timbered or covered with underbrush, into which they were
called to penetrate and engage in that kind of warfare significantly
called bushwhacking. For this service their light draught, not
exceeding three feet when deep, and diminishing to eighteen or twenty
inches when light, peculiarly fitted them; but they were also useful
in connection with the operations of the larger vessels, and some of
them generally went along as a kind of light force fitted for raids
and skirmishing.

The other vessels, which were not completed till later, were of an
entirely different kind, being intended to supply a class of fighting
ships of superior power, armor, and speed to those which had fought
their way down to Vicksburg from Cairo. The fighting power of the
Confederates had increased, and the successes of the Union arms, by
diminishing the extent of their line to be defended, had enabled them
to concentrate their men and guns. The defences of Vicksburg, both on
the Mississippi and Yazoo, had become greatly stronger. The new
armored vessels that were ready for some part of the coming operations
were the Lafayette, Tuscumbia, Indianola, Choctaw, and Chillicothe. Of
these the Tuscumbia, of 565 tons, the Indianola, of 442, and the
Chillicothe, of 303, were specially built for the Government at
Cincinnati. They were side-wheel, flat-bottomed boats, without keels;
the wheels being carried well aft, three-fourths of the entire length
from the bow, and acting independently of each other to facilitate
turning in close quarters. The Indianola and Tuscumbia had also two
screw propell