inventor hezekiah bradford of philadelphia invented a "method of saving floating material in ore-separation” and received us patent no. 345951 on july 20, 1886. he had received his first patent in 1834, primarily invented machinery to separate slate from coal during the 1850s-1860s, and invented the bradford breaker, currently in use by the coal industry. his "bradford ore separator," patented 1853 and subsequently improved, was used to concentrate iron, copper and lead-zinc ores by specific gravity, but lost some of the metal as float off the concentration process. the 1886 patent was to capture this "float" using surface tension, the first of the skin-flotation process patents that was eclipsed by oil froth flotation. it is uncertain if his 1886 patented "flotation" process was successfully introduced.