In 1645, the Undertakers wrote to Winthrop informing him that Richard Leader, a merchant from Salehurst who was familiar with the iron making process, would replace him as manager of the Iron Works. After arriving in Massachusetts, Leader reviewed the previous site survey and looked into some other locations. He selected a location in Lynn, Massachusetts (now part of present-day Saugus) on the Saugus River. The river was navigable for shallow draft vessels and could be dammed to power machinery. The surrounding forests could be used to make charcoal. Bog ore could be mined from nearby ponds, swamps, riverbeds, and bogs. Limestone, which was normally used for flux, was not available, but through trial and error it was found that gabbro, which could be mined in nearby Nahant, would work as a flux.