|Fenian Ram Interior Photos / 02CompressedAirGunHatch
Joseph Costa, Paterson Museum Curator of Photography
At center is the loading hatch for the compressed air gun. A crewman would load the projectile into the tube. The hatch would then be closed and the chamber flooded. A conical cap at the front of the tube would be swiveled open then the crewman would open a valve releasing 400psi of compressed air into the tube to fire the projectile. On Gary McCue's page it's said that the projectile came out of the water 8 or 10 feet from the tube and leaped 60-70 feet into the air before plunging back down into the river, burying itself in the mud. It's still somewhere in the bottom of the river today.
Holland did more test firing of the pneumatic gun and determined that the volume of air following the projectle out the barrel was tipping the rear of the projectile down and throwing off it's aim. By drilling a hole in the barrel close to the muzzle and adding a cavity to vent the excess compressed air as the projectile left the barrel Holland was able to solve the problem and get the pneumatic gun shooting straight.
At the lower left is the compressed air reservoir. The compressor itself has been removed and would have been secured by nuts on the verticle studs on top of the reservoir.