Jane,
You are right on about boilers.
I've been a fire bug all my life fooling with steam boilers and cannons and such.

Here's one I built back around 1985.
The state boys do want to come and watch me pump her up, and then steam her up once a year.
About cannon.
Probably the most famous cannon to blow up was the Swamp Angel in the Civil War.
She was an eight inch Parrott firing 160 pound rifled slug, or shells, at Charleston South Carolina. After 36, or was it 37 shots she blew up.
The Parrott as you know was a cast iron gun with a wrought iron collar shrunk around near the breach of the gun. The cast iron broke inside the collar and the breach went by by.
We all know this hobby has some risk, unless you set your gun by the fireplace to never move it.
But then again, a very experienced bicycle rider in my club bought the farm a couple weeks ago t-boned by a mini van.
Everything has risk, and those with cast guns have to be especially careful
not to be a cowboy with your gun. Find a safe charge, and stick to it.
Oh yea Jane, Where did you get your hat? My wife would look hot in one too.
Thanks,
kap pullen