Scharf on the bombardment of Forts Jackson and St. Phillip:

The next day, April 18, the mortar boats were placed and commenced firing on Fort Jackson. This was possibly the first instance in warfare of blind firing of artillery based on aiming the weapon from a known surveyed location at a target with known survey coordinate points.Over the next six days, thousands of mortar shells poured into the fort. If remaining at one point too long, the Confederates would eventually discover the location of the mortar boats; to avoid this, they were moved with great regularity. This necessitated additional surveying. During this work, "One of the vessels on which Mr. Harris was engaged was struck by a round shot and another vessel where Mr. Oltmanns was in a boat alongside was sunk while he was speaking with the captain." ( This was the schooner MARIA J. CARLTON.) On April 23 Farragut sent the SACHEM downstream to deliver wounded men to Pilot Town, at the entrance of Southwest Pass, as he planned to run past the forts early on the next morning.

Farragut commenced moving the fleet past the forts at 2:00 A.M. on the morning of April 24. Unfortunately, in spite of a bombardment in which over 4,400 shells had burst in or over Fort Jackson out of 7,500 fired, many guns were still operational at both Forts Jackson and St. Philip. The problem was not accuracy, but the fuses of the shells. "Primitive fusing caused the shells either to explode prematurely (thus delivering an ineffectual shower of iron fragments) or, if the fuse had lengthened, to fire the charge only after it had landed. Since the ground in and around both forts was muddy, this often resulted in little more than a muffled roar, followed by a splattering of mud." (Farragut signed off on fuzes too great in burning duration.HW)In spite of this problem, the disruption to the operations of the forts was great. No ships were sunk by the guns of the forts (1 mortar boat was sunk by fire from a rifle. HW)and only 37 men were killed and 146 wounded as Farragut's vessels passed by. This was a light casualty total for the capture of New Orleans, the major city on the Gulf Coast, and the South's loss of access to the lower Mississippi River.

Commander Porter wrote to Bache concerning the battle of Forts St. Philip and Jackson: "... The results of our mortar practice here have exceeded anything I ever dreamed of; and for my success I am mainly indebted to the accuracy of positions marked down, under Mr. Gerdes' direction, by Mr. Harris and Mr. Oltmanns. They made a minute and complete survey from the 'jump' to the forts, most of the time exposed to fire from shot and shell, and from sharpshooters from the bushes.... The position that every vessel was to occupy was marked by a white flag, and we knew to a yard the exact distance of the hole in the mortar from the forts.... Mr. Oltmanns and Mr. Harris remained constantly on board to put the vessels in position again when they had to haul off for repairs, or on account of the severity of the enemy's fire." Porter then pays the highest possible compliment to these men and Gerdes: "...I assure you that I shall never undertake a bombardment unless I have them at my side." Porter also pointed out another aspect of the work: "Mr. Gerdes has been indefatigable in superintending the work, laboring at night in making charts and providing the officers in command of ships with them, marking the positions of obstructions in the channel, and making all familiar with the main way. No accident happened to any ship going through, notwithstanding the gentlemen in the forts thought the obstructions impassable...."

Then it was "On to Vicksburg", with Mortar Schooners in tow.