The last set of batteries, of those erected prior to the bombardment that began on August 17, 1863, that I have to discuss are two mortar batteries among the “left batteries” on Morris Island.
Battery O’Rorke was one of the original works constructed prior to the July 17 assault. As mentioned before, the battery took advantage of earlier work done by Confederates in that sector. The layout had two galleries, with two mortars each, and a bombproof magazine built into the right flank.
Just as during the July bombardment, in August Battery O’Rorke contained four 10-inch siege mortars. These could range the 1,900 yards to Battery Wagner, but not beyond to Battery Gregg or Fort Sumter.
Somewhat counter-intuitive, Battery Kirby sat farther back from the line but was employed against Fort Sumter. While the 10-inch siege mortars had a range of 2,100 yards, the seacoast mortars of the same caliber had the range of 4,250 yards with 10 pounds of powder according to the pre-war ordnance manuals. Later, wartime manuals, list increased charges up to 12 pounds giving a range of 4,536 yards.
Lieutenant Peter Michie recorded laying new platforms for the 10-inch siege mortars on August 12. A single, crowded gallery contained two 10-inch seacoast mortars and one 10-inch siege mortar.
The battery made good use of the line of the dune. Behind the mortars were both a bombproof magazine and a bombproof shelter. First Lieutenant Charles Sellmer commanded a detachment of the 11th Maine Infantry manning Battery Kirby. The battery stood 4,400 yards from Fort Sumter; 3,000 yards from Battery Gregg; and 1,960 yards from Battery Wagner.
Seacoast Model 1840 mortars appear in photographs taken on the “extreme left” of the Federal line:
Another photo from Morris Island also shows the Model 1840 mortars.
Taking allowances for different angles in the photograph, this may also be Battery Kirby. My research leads me to say this is not Battery Kirby. (And that question aside, this is another interesting photo with respect to the details such as aiming stakes.) Regardless, these two photos establish the presence of Seacoast Mortars Model 1840 on Morris Island.
But what about this photo? (Also not Battery Kirby.)
Those appear to be 13-inch Seacoast Mortars Model 1861. I say that based on the arrangement of elevating lugs. Furthermore reports from 1863 indicate the Department of the South had a dozen 13-inch mortars on hand. However, I entertain the possibility 10-inch Seacoast Mortars Model 1861 were present on Morris Island. Why would I split hairs over a model number? Because Cyrus Alger cast only eight of those 10-inch Model 1861. Any service history of such a rare type would be noteworthy.