During July 1840, Perry conducted a series of experiments on the _Fulton_, to determine the effect on the ship’s timbers of the firing of heavy ordnance across the deck of a vessel. The introduction of pivot guns on board men-of-war, rendered these experiments of great value. The bowsprit and bulwarks removed, and the eight-inch Paixhans placed in the middle part of the forward cross bulwarks, thirty feet of the _Fulton’s_ deck was exposed to concussion. Thirty-four rounds fired at a target on shore, showed that every discharge produced an upheaval of the deck. Empty buckets reversed and placed at various distance and positions on the deck approaching the gun, were upset, kicked into the air, destroyed, or shaken overboard. The ease with which men could be killed by the windage of the balls, was demonstrated. A stout cask twelve feet forward of the gun but out of line of fire was knocked overboard. A glass phial which was hung three feet above the cannon’s muzzle withstood the shock, but three feet forward at the same elevation was shattered. Tarpaulin of two thicknesses fastened over a scuttle was rent, and pine boards securely nailed withstood only two or three firings. Perry at once gave the natural explanation that the expansion, pressure, and sudden contraction of the gases generated by the gunpowder, caused the air of the hold to rush up to fill the vacuum, and thus pressed upon the planking of the deck. The heavily built _Fulton_ could resist, where a weaker vessel would start her planks, just as a fish brought up in a trawl from deep-sea beds, bursts when coming to the air. He suggested that any slightly built vessel could be rendered safe, simply by flooding the decks with three inches of water. This he demonstrated after many curious and interesting experiments, thus adding to the sum of knowledge which every naval officer, in the changed conditions of warfare, ought to obtain. Perhaps no finer illustration of the value and power of pivot guns was ever given than upon the _Kearsarge_ when sinking the _Alabama_. Yet of that very ship, the British newspapers had said, “Her decks cannot withstand the concussion and recoil of her heavy guns.” They were evidently unaware of the knowledge obtained by Perry on the _Fulton_, and applied by American builders of our men-of-war. CHAPTER XVII. THE SCHOOL OF GUN PRACTICE AT SANDY HOOK. THE French Navy was at this time leading the British in improved ordnance. A French man-of-war of twenty-six guns was armed entirely with cannon able to fire “detonating shot.” She was reckoned equal to two old line-of-battle ships. Her visit to American ports created great interest among our naval officers, and the Navy Department awoke to the necessity of improving our ordnance.