Monday, August 24.-From the salient of the redan to the end of the ridge occupied by the enemy's pickets and sharpshooters is a distance of 25 yards. Intermediate is a strip of low, wet ground, submerged at spring tides, which will render it very difficult, if not impossible, to continue the sap in this direction under a severe fire.

To-day last night's work was strengthened and perfected. Three Coehorn mortars were put in battery in the fourth parallel, and a bomb-proof magazine for their service begun. This afternoon a mortar was opened on our fourth parallel from Wagner. Three sappers were wounded by it. This mortar proved to be a great annoyance. Its fire was directed on the head of the sap, was very accurate, and our sappers had no shelter from it. Six such mortars well served would, I think, have stopped our work at this period, until subdued by our superior fire. This night the full sap was started from the salient of the redan, being the prolongation of its left face. It had been carried forward but a few yards, when a severe rain storm filled the trench with water, which could not be drained off because the ground was too low; the work, in consequence, made very little progress. The enemy were so near (not more than 20 yards distant) that it was impossible to employ the flying sap.

Captain Graef, on duty in the second and third parallels to-day, reports:

The platform of 8-inch Parrott rifle, gun Numbers 1, Battery Brown, had settled in the rear 9 inches, so that the gunners were afraid to fire the gun. I raised it level. The other platform will have to be raised in the same manner, after a few more days' firing.

This is occasioned by the recoil of the gun, which causes the front of the platform to spring up. The dry sand running under, prevents it from settling back to its original position. Captain Graef continued work on the mortar battery in the third parallel. Lieutenant Farrand followed him, and finished the battery and magazine, and reported it ready for its armament this evening. He also widened the trench leading to the third parallel, to admit the passage of a sling-cart. These mortars were mounted during the night.

Lieutenant J. S. Baldwin this night built a causeway over the marsh, from the boom across the large creek on the left of the second parallel, about 370 feet in a northwesterly direction, to the second creek. A platform was built at the farther end, and a light traverse for the accommodation of a grand-guard outpost.

Captain Pratt's detail completed the bomb-proof magazine in the fourth parallel, and built a barbette emplacement for a Requa battery near the center of the same. He reports that "the severe rain and intense darkness" interfered greatly with the progress of the work. One boat howitzer was mounted on the left of the fourth parallel, making the armament of this parallel three light defensive guns and three Coehorn mortars.

Tuesday, August 25.-Some sharpshooters, who occupy pits just in front of the left of the fourth parallel, annoy us greatly. They are on lower ground than we; hence are enabled to see when our loop-holes are darkened by the heads and rifles of our sharpshooters. In order to flank, and thus dislodge this trouble some enemy, an attempt was made this morning to prolong the right face of the redan from the salient; but the mortar fire, and, what was worse, the water which constantly filled the trench as it was dug, rendered the progress so slow that the enemy had time to protect his its against us.

Experience now proves that the sap cannot proceed farther unless