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 space of ground to each prisoner was only 98.7 feet, or less than seven square yards.  The Federal prisoners were gathered from all parts of the Confederate States east of the Mississippi, and crowded into the confined space, until in the month of June the average number of square feet of ground to each prisoner was only 33.2 or less than four square yards.  These figures represent the condition of the Stockade in a better light even than it really was; for a considerable breadth of land along the stream, flowing from west to east between the hills, was low and boggy, and