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John A Dahlgren and one of his guns.
Prior to the advent of steam propulsion, warships were powered by the wind. This meant that since each side in a battle had to use the same wind, the most effective way to bring guns to bear on the enemy was by use of a broadside as the ships moved parallel to one another. This actually where the term “ship of the line” comes from, as the larger ships of opposing forces would form a line and sail past each other while blasting away. In this situation ships carried every more and larger cannon, to increase their effectiveness. Against wood hulled ships the large solid shots that traditional cannons fired were effective, but there was room for improvement. In 1823 the French general Henri-Joseph Paixhans seized upon this room when he created Paixhan guns, which were the first cannons to be able to fire an explosive shell with a flat trajectory. The Paixhan guns accomplished this by using an explosive shell that was protected by a sabot. The wooden sabot took the force of the firing charge and allowed the shell to be safely lit when the gun was fired without risking a premature detonation. These new guns were very destructive to wooden ships and helped to launch the push for ironclads.
The other obstacle that cannons had to overcome during the antebellum period was their propensity to burst. This became ever more important as cannons got bigger and bigger, and would become a subject of national attention after the Princeton disaster. The Princeton was a steam sloop designed by John Ericsson and Robert f. Stockton. She had two pivot guns one fore, designed by Stockton, and one aft, designed by Ericsson, both guns were 12 inchers that could fire a 225 lb shot 5 miles. However, they did have differences in construction; Ericsson’s gun used pre-tensioning iron bands to reinforce the breach of the gun, making it stringer and lighter. Stockton’s gun was an attempt to copy Ericsson’s gun, but to be different he used more wrought iron in the breach, rather than the pre-tensioning bands. Wrought iron of the day could not withstand the transverse force that was created by the firing of the powder charge in the cannon, this led to small cracks developing over time and eventually the gun would burst. Bursting guns were very common at this time, but the physics of a canon were not well understood, so it was just accepted that eventually a gun might burst. This was no longer an acceptable stance after the Princeton disaster. During a celebratory cruise aboard the newly completed ship, Stockton’s gun, known as the Peacemaker and the largest naval gun in existence as it was several tons heavier than its sister gun, burst, killing 7 and injuring 20 others. Among the dead were Abel Usher, the Secretary of State, Thomas Gilmer, the Secretary of the Navy, and David Gardiner, President Tyler future father in law. Tyler himself only escaped death in the explosion because his fiancée was cold and wanted to stay below decks. This incident brought the issue of cannons bursting to the national forefront, and led indirectly to John Adolphus Bernard Dahlgren’s quest to design more scientific cannon. John A. Dahlgren began expierimenting scientifically with cannons in 1847 when he was stationed at the Washington Naval yard. He used pressure gauges, inserted at different points along a cannon, to measure the forces that were created by firing a cannon and map out there effects. In this project he had a dual purpose, he wanted to make cannons safer and more reliable, and he also wanted to improve on Paixhan gun design by making it more accurate and able to fire solid shot as well as shells. The design that he came up with was the Dahlgren gun, which was rounded and smooth unlike traditional cannons, and carried a greater portion of its weight in the breach. These guns looked like soda pop bottle and were given the name “pop guns”. Don’t let the name fool you, they were the most effective cannon ever built. Dahlgren’s guns were capable of firing solid shot or shells, had significantly better range and accuracy than paixhan guns, and none ever burst in combat.