150 years ago: Confederate engineers considering forensic ballistics

On this day (February 17) in 1864, Confederate engineer Captain R.H. Lucas provided this report:

Charleston, February 17, 1864.
Col. D. B. Harris,
Chief Engineer of Department:
Colonel: In obedience to your order I have just measured the angle at which the enemy’s shell penetrated the house No. 65 King street. I obtained access to upper story and found the perpendicular height from floor to point of entrance 9 feet 10 inches, and on the floor to point of exit, 9 feet 10 inches. This shell appears to have been a 100-pounder. I have measured also several in the market, where the resistance was very slight, and find them as follows:

One 100-pounder, perpendicular height 17 feet 7 inches, base line 16 feet 10 inches, 47° 45″.
One 100-pounder, perpendicular height 19 feet, base line 18 feet, 48° 15″.
One 30-pounder, perpendicular height 13 feet, base line 8 feet, 58° 30″.
One 30-pounder, perpendicular height 14 feet, base line 10 feet, 55°.

I have the honor to be, colonel, very respectfully, your obedient servant,

R. H. Lucas,
Engineer City Defenses.

The measures provided indicate the point at which a projectile hit a structure (perpendicular height); where the projectile was expected to hit the ground (base line) had it proceeded from there unimpeded; and angle of entry.  Would be nice to have a wartime photo of 65 King Street to match with the recorded damage.  But I don’t know of any.

The information presented begs the question: Why were the Confederates concerned with the impact angles of the Federal shells?

The effort was not to help pinpoint Federal batteries.  Lucas did not record azimuths in his data.  Besides, the Confederates could easily see the origin of these shells from their observation posts watching Morris Island.

However, coupled with the known ranges from Morris Island, the data gathered by Lucas offered an indication of the ballistic performance of the Federal guns.  In short, clues to the gun’s performance.  The inclusion of two different calibers (100-pdr and 30-pdr) is worth noting in that regard.

My take?  I think Lucas was tasked with gathering data to match with Confederate weapons tests.  General P.G.T. Beauregard had plans to unleash his own long range artillery fire, using using weapons fired at high angles delivering phosphorus shells.  As mentioned earlier, Confederates had tested obsolete weapons for this purpose.  And on February 10, Beauregard briefly mentioned intentions to use damaged weapons for similar purposes, in communication with his second in command, Major-General J.F. Gilmer:

Has Commander [William W.] Hunter reported yet whether he could transfer to you the Brooke 6.40 gun which had its muzzle shot off? As soon as you get the gun have it properly cut off and banded. I will send you from here a bed for it. This gun is intended to be used, as you are already informed, against the enemy’s naval depot, shops, &c., in Scull Creek near Hilton Head.

The Federal guns had already demonstrated the capability to fire effective payloads over similar ranges.  So I think the Confederate authorities were looking for data to compare with their tests.

(Citations from OR, Series I, Volume 35, Part I, Serial 65, pages 594 and 617.)

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