Define "Explosion" (Part One)

As long as we're discussing 18th-century artillery, we had to think about the question, What is an explosion?  The basic act of placing an antacid tablet in an old-fashioned film canister half-filled with water taught us that an explosion is something getting really big really fast.  That's a simple definition, but it gave us a better idea of what happens at the back end of a musket or one of those cannons Colonel Henry Knox absconded from Fort Ticonderoga to help George Washington and the Continental Army finally secure Boston.