Holding something that resembled an oil can, Preston said that if it were placed in the gleaming barrel of the Model 1857 Light 12-pound Gun-Howitzer, "it can take out men by the dozens."
Another type of projectile, filled with smaller iron balls and an explosive charge, would basically leave the human form "unrecognizable," Preston said.
Preston said field officers in the Civil War often described the "pink haze" over the battlefield, which would be a mixture of gun smoke and the spray of exploding ordnance and humans.
The lecture was supplemented by an educational firing of the two-ton howitzer.
Preston explained the role of each one of the men firing the howitzer, as well as what dangers they might have faced in wartime - including misfires, failed cannon barrels, errant sparks, lost limbs and the rain of oncoming bullets.
But the actual firing of the howitzer - aside from the boom - was an orderly and peaceful demonstration.
One man brought a round from the ammunition box 30 feet to the howitzer. Another man took it from him and hoisted it into the cannon. Another rammed the round into the cannon. A fourth kept cover over an important airway into the cannon.
The corporal took aim, gave the OK, everyone took cover, the corporal said "Fire!" and the trigger man pulled the cord, freeing the spark that lit the charge, eliciting a single boom that echoed into the valley.
"Isn't that cool," Preston said with a grin.
After the demonstration and lecture was over, Marion Hoffer, 49, of Lancaster County, Pa., said she was a little awestruck.
"It's hard to believe that this is how battles were fought," Hoffer said.
Her husband, Barry Hoffer, 52, said, he felt similarly:
"We just survive doing what we normally do, and not trying to prevent from being killed."