Adam Badeau, Military history of Ulysses S. Grant from April 1861 to April 1865. Volume 1

After the assault of May 22d, the enemy's defence was feeble. As the national batteries were built and opened, the rebel artillery-fire slackened, until, towards the close of the siege, it was hardly employed at all; the enemy contenting himself with occasionally running a gun into position, firing two or three rounds, and withdrawing the piece again as soon as the national fire was concentrated in reply. At almost any point, if the rebels had put ten or fifteen guns into position, instead of one or two, which merely invited concentration of the besiegers' fire, they might have seriously delayed the approaches. This silence of the artillery was attributed to a lack of ammunition; but a judicious use of the ordnance which the rebels really possessed would have interfered greatly with Grant's operations. As it was, he had little but musketry-fire to contend with in the more distant approaches and parallels, and even this was sparingly used, in comparison with that of the besiegers: a deficiency in percussion caps probably accounts in some measure for this fact.

The enemy sometimes resorted to mines, to delay the approaches of Grant; but they were feeble, their charges always light, and they rarely did other damage than to make the ground where they had been exploded, impracticable for mining by the besiegers. Occasional sorties were also made, sometimes delaying operations for a day or two. At one point, the enemy opened ninety yards of trench, as a counter-work, running down the ridge from a rebel salient, and quite up to the parallel of the besiegers. But the position was recovered the next night by a