These are intended for offense and defense. If the inner Stockade should
at any time be forced by the prisoners, the second forms another line of
defense; while in case of an attempt to deliver the prisoners by a force
operating upon the exterior, the outer line forms an admirable protection
to the Confederate troops, and a most formidable obstacle to cavalry or
infantry. The four angles of the outer line are strengthened by
earthworks upon commanding eminences, from which the cannon, in case of
an outbreak among the prisoners, may sweep the entire enclosure; and it
was designed to connect these works by a line of rifle pits, running
zig-zag, around the outer Stockade; those rifle pits have never been
completed. The ground enclosed by the innermost Stockade lies in the
form of a parallelogram, the larger diameter running almost due north and
south. This space includes the northern and southern opposing sides of
two hills, between which a stream of water runs from west to east.
The surface soil of these hills is composed chiefly of sand with varying
admixtures of clay and oxide of iron. The clay is sufficiently tenacious
to give a considerable degree of consistency to the soil. The internal
structure of the hills, as revealed by the deep wells, is similar to that
already described. The alternate layers of clay and sand, as well as the
oxide of iron, which forms in its various combinations a cement to the
sand, allow of extensive tunneling. The prisoners not only constructed
numerous dirt huts with balls of clay and sand, taken from the wells
which they have excavated all over those hills, but they have also, in
some cases, tunneled extensively from these wells. The lower portions of
these hills, bordering on the stream, are wet and boggy from the constant
oozing of water. The Stockade was built originally to accommodate only
ten thousand prisoners, and included at first seventeen acres. Near the
close of the month of June the area was enlarged by the addition of ten
acres. The ground added was situated on the northern slope of the
largest hill.

The average number of square feet of ground to each prisoner in August
1864: 35.7

Within the circumscribed area of the Stockade the Federal prisoners were
compelled to perform all the offices of life--cooking, washing, the calls
of nature, exercise, and sleeping. During the month of March the prison
was less crowded than at any subsequent time, and then the average