screw propeller As a 20-year old, John Ericsson (1803‒1889) devoted all his free time to his inventions, among which was a hot-air engine. In 1826, unable to find anyone to finance his engine, he traveled to the UK. There he had difficulty getting the engine to work properly because the heat produced by English coal was too intense. Ericsson shifted his focus and produced a new type of steam boiler, the “tube boiler,” which he used in constructing his “Novelty” locomotive, which competed against George Stephenson’s “Rocket.” Ericsson’s locomotive was faster, but due to damage it could not compete in the final, decisive stage of the contest. Ericsson’s many developments included hot-air and steam engines and solar heaters, but his most important work as an inventor was in the area of propellers for ships. While Ericsson was not the first to construct a propeller, his design for driving ships was the first practical one. Propellers have barely changed in appearance since Ericsson presented his design. Following his successes with propeller design and innovative steam engines, Ericsson focused once again upon the construction of hot-air engines. He made significant progress and in 1865 he received a patent for a
small, easily-maintained machine which could operate on different types of fuel. The engine was a success and made Ericsson financially independent. Ericsson gained his greatest fame for building the Monitor, the Union Navy’s armored warship which conquered the Confederate navy’s Merrimac during the American Civil War. The Monitor was 52 meters long, 12 meters wide and clad entirely in plate iron. Of the Monitor only the deck, two canons in a rotating gun turret, the command bridge and the smokestacks were visible above the surface of the water. The ship was completed on January 30, 1862 and on March 4, the battle between the Merrimac (armed with ten fixed guns all around) and Ericsson’s Monitor took place at Hampton Roads in Chesapeake Bay. The Merrimac was unable to damage the smaller ship and was forced to retreat. The success of the Monitor was a contributing factor to the establishment of the Union navy’s dominance at sea. Over 100 warships were built using this design, including four for the Swedish navy. The only wellpreserved Monitor-type ship in the world is the Sölve, which can be seen today at the Maritime Museum in Gothenburg.
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