At the Cliff Mine are preserved some curious specimens of ancient copper tools found in its vicinity, but it is to the westward of the Keweenaw Peninsula that the most extensive traces of the aboriginal miners’ operations are seen. The copper-bearing trap, after crossing the Keweenaw Lake, is traced onward in a south-westerly direction till it crosses the Ontonagon river about twelve miles from its mouth, at an elevation of upwards of three hundred feet above the lake. At this locality the edges of the copper veins crop out in various places, exposing the metal in irregular patches over a considerable extent of country, many of which have been partially wrought by the ancient miners. Here, in the neighbourhood of the Minnesota Mine, are extensive traces of trenches and other mining operations, which prove that they must have been carried on for a long period. These excavations are partially filled up, and so overgrown in the long interval between their first excavation and their observation by recent explorers, that they scarcely attract attention. Nevertheless some trenches have been found to measure from eighteen to thirty feet in depth; and one of them disclosed a detached mass of native copper, weighing upwards of six tons, resting on an artificial cradle of black oak, partially preserved by immersion in the water with which it had been filled. Various implements and tools of the same metal also lay in the deserted trench, where this huge mass had been separated from its matrix, and elevated on the oaken frame, preparatory to its removal entire. It appeared to have been raised about five feet, and then abandoned, abruptly as it would seem: since even the copper tools were found among the accumulated soil by which it had been anew covered up. The solid mass measured ten feet long, three feet wide, and nearly two feet thick; every projecting piece had been removed, so that the exposed surface was left perfectly smooth, possibly by other and ruder workers of a date subsequent to the desertion of the mining trench by its original explorers.