Yes, I think some other posters got it right. This was a shell, not a cannon ball. Any Civil War experts out there? is the Civil War the first one to use shells?
I can’t recollect but I think I saw a documentary where the French Navy was developing shells just before the civil war.
I may be wrong.
"In addition to solid spheres of stone, lead, or cast iron, bombs or shells could also be fired from mortars, and later became quite popular, especially as an antipersonnel weapon. They were not usually fired from cannon until later. A bomb was a hollow sphere of cast iron with a port into which a fuze could be hammered."
"Shells are said to have been used at the sieges of Naples in 1495 and of Wachtendorf in 1588. Henry VIII is reputed to have had mortars and bombs made by foreigners in 1544, and by 1634 they were in common use by the Dutch and Spanish. Of course, bombs could be as effectively thrown by catapults as by cannon. Incendiary bombs had been known since antiquity." From this site on cannons