The Confederate Military Prison at Andersonville, Ga., consists of a strong Stockade, twenty feet in height, enclosing twenty-seven acres. The Stockade is formed of strong pine logs, firmly planted in the ground. The main Stockade is surrounded by two other similar rows of pine logs, the middle stockade being sixteen feet high, and the outer twelve feet. 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 earth-works 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 zigzag, 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 oxide of iron, which form, 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 portion 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 on the northern slope of the largest hill. 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.