Reports, 1923-1925, of diamond drilling at various sites in Michigan's Upper Peninsula, including Cherokee, Clark, Copper Range, Keweenaw Copper, Mass, Naumkeag, New Baltic, Oneco and Torch Lake mines. The field work was done by both Calumet and Hecla Consolidated Copper Company's Geological Division and the United States Geological Survey, probably in support of Professional Paper 144, "The Copper Deposits of Michigan."