10 August (morning)
As dawn breaks, the Royal Navy force opens fire. They concentrate almost entirely on the outer layer of Charleston defences - Fort Wagner, Fort Gregg, Fort Chatfield and Fort Beauregard being the largest and most prominent.
Fort Gregg is hit hard by the very first shot, the one-ton mortar shell of Superb's mortar, and one of its own seacoast mortars never even manages to fire as it tumbles into the crater left by the shell.
After the initial surprise has worn off, the Charleston forts return fire - mostly the outer layer in question, but Fort Sumter has two heavy rifles on the barbette and they can see some of the attacking enemy (though the range is long - well over two miles). The two rifles are not very much in comparison to the avalanche of fire hitting the various outer ring forts, but they do make the Sumter gunners feel better.
In comparison to the masonry works that mostly formed the defences in the Trent War, the earthwork construction of the Charleston batteries makes them somewhat better at resisting the British fire. This is a purely relative matter - the Armstrong 110 pounder is able to put shell right though even the base of the walls - but internal bursts merely move the earth around rather than having a shattering effect, reducing the extent to which heavy fire results in a complete collapse.
Fort Wagner scores two hits in quick succession on HMS Falcon with 10" and 8" seacoast guns, and the damage cuts down the mainmast and fouls the sloop's guns. She withdraws in obvious difficulty, a cheering moment for the whole of the defenders - though one marred a few minutes later when the Great Eastern's broadside firing at extreme range disables the 32-pounder gun on the barbette.
The Pisces also takes a hit, this time from one of the seacoast mortars, and discovers to the dismay of the crew that the Confederacy have at least a few of Martin's Shell. The fire takes some twenty minutes to extinguish, disabling the Zodiac class ironclad for half an hour and resulting in a reduction in performance afterwards, and would have been a more serious problem had the hit not been right forward and much of the molten iron not gone into the sea.
At about nine in the morning, there is a shattering explosion as a shell reaches the magazines of Fort Chatfield at Cummings Point - taking advantage of the damage already done by mortar fire. Several tons of gunpowder go up, and the entire fort heaves up before collapsing into the crater.
This causes a long pause, then firing begins again - somewhat less effectively on both sides, as smoke and fatigue begin to tell.
Within another thirty minutes, the liner Victoria is ordered to leave the line. Owing to her large size and aggressive handling, she has been the focus of much smoothbore battery fire, and this has included three or four hot shot which struck almost together. The result of this is a fire on the gundeck, and Stopfort orders her in no uncertain terms to withdraw out of range until she is no longer actually ablaze.
By the hour before noon, the outer batteries of Charleston have been effectively neutralized, though not without cost - in addition to the Falcon's damage and the near loss of the Pisces, both the Snipe and Steady are listing and have taken significant casualties (the Snipe was unlucky to have an 8" shell burst just before it would have hit, showering the light gunboat with shrapnel) and the liner Victor Emmanuel has a particularly well aimed 7" shell lodged in her scuttles - though fortunately for the crew, and in particular the handlers, the shell's fuze turns out to be improperly fitted. (Incidentally, later in life many of the belowdecks crew of Victor Emmanuel will be unusually devout.)
Several other ships have taken more minor damage, and the Royal Oak has a hole in her funnel near the top.
Three of the transports with the RN fleet begin landing troops to the south of the disabled Fort Wagner, intending to take Cummings Point to set up Armstrong batteries on it.
This causes debate in Charleston, where Ingraham is trying to work out when to commit his ships. Some of the more hotheaded miltia officers are demanding he send the ironclads out now, though he points out the (entirely reasonable) point that none of them will last very long with the entire Royal Navy squadron firing on them.
Instead, the idea of sending the ships in when the Royal Navy enters the harbour (as they must, he feels) appeals to him more. Perhaps this is partly because it means delaying the moment, or because Fort Sumter is actually armed as well as a fairly major ship of force.
On board the Royal Navy flagship (Royal Oak), Stopfort examines the reports he has had so far over lunch. Victoria's situation is unfortunate, and he considers pausing for the day, but his overall opinion is that it is important to ensure the batteries cannot be re-established overnight.
The next stage of the defences includes the best armed forts, though they are pre-war forts and as such share the weaknesses of all masonry forts - Sumter and Moultrie - and a number of batteries established either side of Moultrie which were not able to bear effectively on the Royal Navy forces during the early bombardment. Stopfort's first instinct is to send his ironclads in ahead as they are invulnerable to most fire, but it is pointed out that there may be mines in the channel and he concurs.
While he does not have any of the Royal Navy's new minesweeper gunboats with him (a considerable oversight) he does have enough gear in the cavernous holds of the Great Eastern to jury-rig something close on the gunboats he does have.
ED: changed the RN flagship to the correct Royal Oak, something I keep forgetting!