sentences:  The failure educated him not to build a costly mill before opening an ore reserve large enough to pay the bills, let alone make a profit.By the mid-1890s, Ricketts was rehired by Douglas and sent to northern Sonora, Mexico, with hopes of finding copper properties.In 1897, Dr. Ricketts recommended that Phelps Dodge buy the then-small Moctezuma (Nacozari) copper mine in northern Sonora from the Guggenheim family.