The district of country called Dubuque's Mines, embraces an area of about twenty-one square leagues, commencing at the mouth of the Little Maquaquity River, sixty miles below Prairie du Chien, and extending along the west bank of the Mississippi River, seven leagues in front by three in depth. The principal mines are situated on a tract of one square league, beginning immediately at the Fox village of Aquoqua, or the Kettle chief, and extending westwardly. This is the seat of the mining operations carried on by Dubuque, as well as of what are called the Indian Diggings. Geologically it is the same formation that characterizes the mines of Missouri; but there are some peculiarities. The ore found is the common sulphuret of lead, with a broad foliated, or lamellated structure, and high metallic lustre. It occurs massive and disseminated, in a red loam, resting on a horizontal limestone rock. Sometimes small veins of the ore are seen in the rock, but it has been generally explored in the soil. It generally occurs in narrow beds, which have a fixed direction; these beds extend three or four hundred feet, when they cease, or are traced into crevices in the rock. At this stage, the pursuit of ore, at most of the diggings, has been abandoned, frequently with small veins of the metal in view. No matrix, so far as I observed, is found with the ore which is dug out of the soil, unless we may consider such an ochery oxide of iron, with which it is slightly incrusted. Occasionally, pieces of calcareous spar are thrown out with the earth in digging after ore. I picked up from one of these heaps of earth a specimen of transparent crystallized sulphate of barytes; but this mineral appears to be rare. There appears to be none of the radiated quartz, or white opaque heavy spar, which are so abundantly found at the Missouri mines.[112] [112] _Vide_ my View of the Lead Mines of Missouri, &c., New York, 1819. The ore at these mines is now exclusively dug by the Indian women. Old and superannuated men also partake in the mining labor, but the warriors and men hold themselves above it. In this labor, the persons who engage in it employ the hoe, shovel, pick-axe, and crow-bar. These implements are supplied by the traders at the island, who are the purchasers of the crude ore. With these implements they dig trenches, till they are arrested by the solid rock. There are no shafts, even of the simplest kind, and the windlass and bucket are unknown to them--far more so the use of gunpowder in the mining operations. Their mode of going down into the deepest pits, and coming up from them, is by digging an inclined way, which permits the women to keep an erect position in walking.[113] I descended into one of these inclined excavations, which had probably been carried down forty feet, at the perpendicular angle. [113] This is believed to be an oriental mode of excavation, which appears to have been practised in digging wells.