Complex sentence: Chinn was then on his way up in mining circles, ultimately becoming general manager of all Pickands Mather mining properties in the Lake Superior region in 1918; he was succeeded as superintendent of the Elba and Corsica mines by L. C. David.
Split into simpler sentences: Chinn was then on his way up in mining circles, becoming general manager of all Pickands Mather mining properties in the Lake Superior region in 1918. He was succeeded as superintendent of the Elba and Corsica mines by L. C. David.