For August 30, 1863, Major Thomas Brooks offered a short entry in his journal:
The unfinished work of yesterday is in progress to-day. As the moon shines brightly to-night, and the enemy are firing constantly, no attempt was made to advance.
Lieutenant-Colonel Purviance, commanding Eighty-fifth Pennsylvania Volunteers, was killed during this tour of duty as commander of the special guard of the advanced trenches, by one of our own shells, which exploded prematurely.
Just a few days earlier, Brooks lamented, because of the inability to advance the siege lines. Now the operation appeared to be in a rut again. Having seized the ridge and opened the fifth parallel just a few hundred yards from Battery Wagner, the engineers encountered a new problem – moonlight. A full moon phase passed during the nights after the assault on the ridge:
- August 27-28: 98% illumination. Moon rise 5:52 p.m. Set 5:31 a.m.
- August 28-29: 100% illumination. Moon rise 6:31 p.m. Set 6:40 a.m.
- August 29-30: 99% illumination. Moon rise 7:09 p.m. Set 7:47 a.m.
- August 30-31: 95% illumination. Moon rise 7:47 p.m. Set 8:52 a.m.
While this allowed the Federals to see better during night operations, the light gave the Confederates a better view of the sap and any movement along the line. On the night of August 29, a well placed shell fired from Battery Wagner killed six in the advanced trenches. The advance of the siege lines would wait until darker nights.
While the Federals waited on the moon, they improved and expanded the fifth parallel.
This parallel offered wider spaces behind tall parapets. This became both staging point and battery. On the far left of the line, upon the ridge, a redan with a Billinghurst-Requa gun covered the front of the line. Along the main line of the parallel was a bomb-proof service magazine, a splinter-proof depot for the engineers, another splinter-proof shelter, and a large bomb-proof magazine. The profile of the later was recorded as line s-s’:
This magazine supported the main armament of the fifth parallel – mortars. Four 10-inch siege mortars went on the center of the parallel. On the far right were three (some say four) 24-pdr coehorn mortars. Later three 10-inch siege mortars went into the left of the parallel. The siege mortars used the same platforms Brooks perfected on the earlier parallels. The proximity of these mortars to the target reduced the risk of friendly fire casualties.
Behind those mortar positions, the engineers placed another parapet. This allowed the infantry to move through the parallel without disturbing the mortar crews… or another way of looking at it, allowed them to avoid the dangerous concentration of gunpowder and shells. Such a “bypass” was not built on other sections of the line and reflected the need to rapidly move troops forward in support of a final rush towards the Confederate works.
On the far right, a large fascine parapet anchored the line on the beach. The structure was ten fascines wide and initially three high. The placement of the fascines allowed crews to move out onto the beach then into position to start the next siege approach line. Eventually another Billinghurst-Requa would occupy a position in that vicinity. But for the time being, the Federals were content to simply have the opening fortified in preparation for the next phase.
While not denoting major advances of the siege lines, Brooks’ report on August 30 was not the sullen entry recorded on the 25th. The Federals were compressing a coil of men and equipment. All they needed was a few dark nights to press forward towards their objective.
(Citation from OR, Series I, Volume 28, Part I, Serial 46, page 298.)