the Dreadnought Mine, already noticed; but from a hasty view, I have considered it as continued north-easterly to the Dodgeville Diggings, and then in a general easterly direction, through the diggings at Messersburg, Porter's Grove and Ridgeway, to those at the Blue Mounds, when it apparently takes a south-easterly direction to Campbell's Diggings, north of Monticello, and the Sugar River Diggings at Exeter. The last form a group of East and Wests, bearing E, S. E., and at first receding east towards the south, thus forming a body of mineral bearing south-easterly The most southern ranges, however, appear to recede to the west; the whole body thus forming a curve. Horou

It may be interesting to notice the different strata in which the mineral has been worked in the diggings examined by me. As the depth to which mining has been carried on has been generally limited by that of the water level, it has rarely exceeded 100 feet, and bas been usually much less; in many instances, only 30-40 feet. Consequently only a small depth of rock has been penetrated in any one instance, and it is thus necessary to judge of the probable downward extent of the mineral by a comparison of different localities, where different strata are brought to or near the surface. This has shown that all the beds of limestone have, in such instances, been found good mineral-bearing rocks, and that the openings succeed each other in regular order, and are connect. ed by vertical veins and mineral crevices, passing from one to the other. When the entire thickness of the upper magnesian is pres

ent, the diggings are confined to its upper bed. As the strata become denuded, they commence in the lower part of the upper bed and extend to the middle bed. When the strata are still more denuded, they commence in the middle bed and extend to the lower or through that to the blue limestone, or they even commence in the lower bed and extend through the blue limestone. It is only towards the northern border of the district, where the lower magnesian is exposed in a deep ravine, that I have observed any diggings in that rock.

In tracing the diggings through the different series, it may be stated generally, that in the Muddy and North Diggings mining has been carried on only in the upper bed of the upper magnesian; in the Beetown Diggings, in the upper and middle beds, and adjoining some valleys and ravines, in the lower bed; in the Potosi Diggings, in the same; in the Brushhill, Whig and Platteville Diggings, in the upper and middle beds, chiefly in the latter; in the Patch, South-East Platteville and North Elkgrove Diggings, in the upper and middle beds, chiefly in the former; in the South Elkgrove and Strawberry Diggings, in the middle bed; in the Menominee, Fairplay and Hazel Green Diggings, also in the Dubuque, Upper Galena and Vinegar Hill Diggings, in the upper bed; in the Benton and New Diggings, in the upper and middle beds, chiefly in the latter in the wide flint openings; in the southeast part of series 3, from Buzzard's Roost to the Shulleburg branch, in the lower bed and the blue limestone, chiefly in the former; in Earnest and Spenceley's and the Shullsburg Dry-bone Diggings, in the lower bed; in the rest of the Shullsburg Diggings, generally in the upper bed, but in those where depth has been gained by draining, as in those at the village and at Town send's, also in the middle bed, at the former in the wide flint openings; in the Blackleg Diggings, chiefly in the upper bed, but in the deep shafts on the large North and Souths, also in the middle bed; in the Wiota Diggings, in the upper and middle beds; in the South Forked Deer Diggings, in the blue limestone; in the North Forked Deer and King's Diggings, chiefly in the lower

bed of the upper magnesian; in the Mineral Point Diggings, in the middle and lower beds of the upper magnesian, and in the blue limestone (in the upper and middle beds.) The blue lime stone is there reached only in those diggings where the rocks are most denuded, namely, towards the south-west, and adjoining the valleys and ravines; in the more northern diggings (at the Dreadnought Mine,) mining is chiefly confined to the middle bed of the upper magnesian. At Dodgeville, adjoining the village, the diggings are in the upper and middle beds of the upper magnesian; at Duke's Prairie, in the same; at the Yellow-stone Diggings, in the two lower beds of the upper magnesian, and in the blue limestone, chiefly in its upper bed; at J. Scott's Diggings, east of Argyle, in the lower part of the upper magnesian, and at H. Scott's, in the blue limestone; in the other diggings in Green Co., chiefly in the middle and lower beds of the upper magnesian, and in a few instances, as at the Aspen Grove Mine, in the blue limestone. It may be just added, that in the Heathcock range (Linden) the mineral has been chiefly worked in the middle and lower beds of the upper magnesian, but has been recently followed into the upper bed of the blue limestone.

Copper ores (the sulphuret and carbonate) have been found in large quantity in the mineral district (south of the Wisconsin) only at Mineral Point. Smaller quantities have been found in other localities, particularly at Lost Grove, west of Mineral Point, and 4-5 miles south of Wiota, but these I have not yet visited. I have already noticed the occurrence of small quantities of copper ore in the openings in the middle and lower beds of the upper magnesian, particularly in the middle bed at Shullsburg, and in the lower bed on Fever river, at Buncomb and north of New Diggings. Traces of copper are said to have been found at the Wolf Diggings (west of Jamestown,) in the upper bed.

The copper ores at Mineral Point occur distinct from the lead ore, in ranges apparently in the same East-West line with cor

responding lead ranges; the same ranges being lead-bearing on the west, and copper-bearing on the east; the lead and copper ores being at the same time more or less intermixed at the point of junction. There are thus presented two bodies of mineral, lead on the west and copper on the east, bearing N. N. Easterly across the bearing of the ranges. The width of the body of copper ore is apparently 1-2 miles. Both the vitreous and yellow sulphurets are found in the rubbish, more or less accompanied with iron pyrites; but as none of the ranges are now worked, their relative proportion cannot be determined. The earth from the openings has a deeper red tint than that from the lead openings, where such a tint would be considered unfavorable. The arrangement of the body of copper ore, in this instance, across the bearing of the ranges is very remarkable, but corresponds with the general transverse arrangement of the bodies of lead ore, already indicated. The copper has been worked here chiefly in the lower bed of the upper magnesian, but occurs also in the blue limestone.

I have already observed that the original ores, in the veins and openings in the mineral district, are apparently the sulphurets, namely, of lead, copper, zinc and iron. These ores are more or less subject to decomposition, and to recomposition into other ores; those of lead least, of iron most so."

7

The sulphuret of lead is chiefly recomposed into the carbonate; the sulphate being rarely observed. The carbonate sometimes forms merely an earthy încrustation on the surface of the sulphuret; but in other instances, the sulphuret is converted to a greater or less thickness, sometimes throughout its entire mass, into the carbonate, still retaining its form unchanged. Sometimes the earthy coat becomes detached and loose, and is then called mineral ashes. In a few instances, the massive carbonate, still re-. taining the form of the sulphuret, has been found in large quantity, forming bunches in the openings or veins; in one instance, it is said, at Potosi, to the amount of more than 7000 lbs. Crystals of

the carbonate are occasionally found, adhering to the surface of the sulphuret, or occupying cavities in it, generally in small quanty, but in some openings more abundant. The largest quantities, I have yet noticed, were in the Aspen Grove Mine, in the blue limestone. The formation of the earthy carbonate on the surface of the sulphuret is apparently going on at present, particularly on the outskirts of the veins. The conversion of the whole or the greater part of the sulphuret to a massive carbonate, and the formation of crystals of the carbonate, appear to be rather the results of former agencies than of those at present operative. The carbonate is called white mineral by the miners, and is more easily reduced than the sulphuret, though yielding a less percentage of lead, but has not yet been found in sufficient quantity to be of much importance.

The sulphuret of copper is recomposed into the sulphate and the carbonate. The former is too soluble and too subject to deż composition to be permanent; the latter generally accompanies the sulphuret as a coating, and sometimes in crystals, but not in sufficient quantity to be important. Both the blue and green carbonate occur, but the latter is most common..:

The sulphuret of zinc is recomposed into the sulphate, the carbonate and the silicate; but the former, like that of copper, is not permanent. The carbonate and the silicate are permanent, and are called dry-bone by the miners. They resemble each other, but the carbonate is most common and the most important. They usually replace the sulphuret (black-jack) without much change of form, the general arrangement of the vein or sheet being retained, but the dry-bone being usually less compact, and sometimes appa rently stalactitic. In such cases, however, it retains very nearly the original form of the sulphuret, which exhibits too the same botryoidal arrangement... Not unfrequently the interior of the dry-bone is found occupied by the sulphuret unchanged. These recomposed ores of zinc are more abundant in some ranges and openings than in others. The sulphuret of zinc has appeared more subject to decomposition in the lower openings than in the upper; and in the lower openings, it will be found little changed in one.