the original method of heating round shot was to cover them in the coals of a large wood fire, or heat them on metal grates placed over a fire pit. these time-consuming methods were improved by the french, who used specially-constructed furnaces to heat shot in their artillery batteries at the mouth of the rhône river in 1794. the united states incorporated hot-shot furnaces into the design of coastal fortifications during the construction of the second system of seacoast defenses just prior to the war of 1812. colonel jonathan williams left his post as commandant at the us military academy to build hot-shot furnace fortifications such as castle clinton and castle williams in new york harbor during this period. when french engineer general simon bernard came to the us in 1816 to head the board of fortifications, for the construction of permanent forts to defend the us coastline, he introduced the idea of hot shot furnaces of the french pattern. the chain of us seacoast forts built between 1817 and the american civil war, such as fort macon, subsequently had one or more hot shot furnaces included as part of their standard defenses.