enough to bear the weight of a man without sinking very much. Nevertheless it adds very greatly to the strength of the work against assault.
The salient of the north bastion is about 140 yards from the river bank, and say 110 yards from the levee, and the river is about 700 yards wide.
In the center of Fort Jackson is a defensive barrack of decagonal shape. It is intended to be made bomb-proof by covering the 1-foot-square timbers of the ceiling with earth. Probably the rebel garrison have done this. This building will accommodate 400 or 500 men. As there is besides a great deal of bomb-proof shelter in the casemates and galleries, the garrison is well sheltered from a bombardment.
FORT SAINT PHILIP.
Fort Saint Philip was partly built by the Spaniards and finished to its present outline by us in 1812-'15. It is very irregular in figure. It occupies a quadrilateral space of about 150 by 100 yards.
The front toward the river (first built) had a bastioned trace; the other portions have been added to inclose the work and give some semblance to flanking arrangements. The brick scarp was originally of slight relief and imperfectly founded; was found in very bad condition when I took charge in 1841., Under my charge the walls were strengthened ny relieving arches, an additional thickness of masonry given to them, the earthen parapets extended all around the work (there having been a mere brick wall as parapet before), and the wet ditch deepened so as to have 6 feet depth at lowest water.
It may be stated, in a general way, that the scarp wall on land fronts has 16 to 17 feet height (from bottom of ditch), and on water fronts about 14 or 15 feet. The part of the ditch next the scarp walls is not more than 2 or 3 feet deep at low water, the deepest part of the ditch being generally nearer the counterscarp. (There is no brick counterscarp; merely board revetment, as at Fort Jackson.)
It was intended to arrange a low glacis with covert way and reverted breast-bight wall around the work, but I believe this has not been done; if not, one-half of the height of the scarps would beseem from outside, and it would require little battering to bring them down. There is a postern and draw-bridge in the western face and another near the most angle of the works.
Two extremal batteries (eathern) have been built of late years in connection with this work, having wet ditches (6 feet at low water), having parapets 20 feet thick, crest 19 feet above bottom of ditch, which is 20 feet wide (at bottom). These batteries were intended for twenty-two heavy guns each on water faces and six 24-pounders on extremities and rear.
The sketch will exhibit the bearing of these batteries and their connection with the main work. It will also exhibit the number of guns of the two forts bearing upon any one point of the river within their range.
The main work of Saint Philip is arranged to receive, say, twenty heavy guns, bearing directly upon the channel, besides some dozen or more bearing upon the land.
This armament of seventy-two channel-bearing guns (fort and external batteries) is all en barbette and very low at that, the crests (or tops) of the parapets being but 14 feet above low water of the river and 9 feet above ordinary high water.
At Fort Jackson there are but sixteen guns in casemate, the remaining