Fort Sumter is a pentagonal structure, built upon an artificial island at the mouth of Charleston harbor, three and three-eighths miles from the city of Charleston. The island has for its base a sand and mud bank, with a superstructure of the refuse chips from several northern granite quarries. These rocks are firmly embedded in the sand, and upon them the present fortification is reared. The island itself cost half a million dollars, and was ten years in construction. The fortification cost another half million dollars, and at the time of its occupancy by Major Anderson, was so nearly completed as to admit the introduction of its armament. The walls are of solid brick and concrete masonry, built close to the edge of the water, and without a berme. They are sixty feet high, and from eight to twelve feet in thickness, and are pierced for three tiers of guns on the north, east and west exterior sides. Its weakest point is on the south side, of which the masonry is not only weaker than that of the other sides, but it is unprotected from a flank fire. The wharf and entrance to the fort are on this side. The work is designed for an armament of one hundred and forty pieces of ordnance of all calibres. Two tiers of the guns are under bomb-proof casements, and the third or upper tier is open, or, in military parlance, _en barbette_; the lower tier for forty-two pounder paixhan guns; the second tier for eight and ten-inch columbiads, for throwing solid or hollow shot; and the upper tier for mortars and twenty-four pound guns. The full armament of the fort, however, had not arrived when Major Anderson took possession; but after its occupancy by him, no efforts had been spared to place the work in an efficient state of defence, by mounting all the available guns and placing them at salient points. Only seventy-five of the guns were in position at the time of the attack. Eleven paixhan guns were among that number, nine of them commanding Fort Moultrie, which is within easy range, and the other two pointing towards Castle Pinckney, which is well out of range. Some of the columbiads, the most effective weapon for siege or defensive operations, were not mounted. Four of the thirty-two pounder barbette guns were on pivot carriages, which gave them the entire range of the horizon, and others have a horizontal sweep of fire of one hundred and eighty degrees. The magazine contained seven hundred barrels of gunpowder, and an ample supply of shot, powder and shells for one year’s siege, and a large amount of miscellaneous artillery stores. The work was amply supplied with water from artificial wells. In a defensive or strategical point of view, Fort Sumter radiates its fire through all the channels from the sea approach to Charleston, and has a full sweep of range in its rear or city side. The maximum range of the guns from Sumter is three miles; but for accurate firing, sufficient to hull a vessel, the distance would require to be reduced one-half of that