Aza Arnold
Born 4 Nov 1788, in Smithfield, Pawtucket
In his younger days he was engaged in the mill business associated with the Slaters, later manufacturing cotton and woollen machinery. He built and operated a mill at Great Falls, N.H. Establishing a machine shop at East Greenwich, he and his sons made cotton machinery. He was an inventor of some note, and perfected a compound motion (differential) for speeders, and also a machine for the manufacture of files. He afterward moved to Philadelphia, where he became interested in the manufacture of print goods. He then made his home in Washington, D. C., where he died in 1865, at the age of 75.[1]
Aza Arnold served his apprenticeship with Samuel Slater. He is credited with inventing the differential gear, which he applied to roving frames for retarding bobbin speed during winding. He first conceived it in 1818, first applied it 1820, and obtained a patent in 1823.[2]