of portance. The survey of the whole State must be the work time; to be yaluable, it should be made deliberately, and as far as possible, in a connected order. As long as I am entrusted with this object, I shall endeavor to give it such a direction, and particularly to make it contribute to develope the great resources of the State. State: 101 soitinnfroggo Toqora ni anoitantie goibnogastros Herewith I have the honor of submitting the following report: Very respectfully, JAMES G. PERCIVAL, 2 4 a State Geologist REPORT. The Mineral District in Wisconsin, so far as I have examined it includes all that part of the State between the Mississippi, on the west, and the valley of Sugar river, on the east, south of the line, already indicated. Small quantities of lead ore are reported to have been found farther east, between Sugar and Rock rivers, and even in the quarry, at Janesville, on the east bank of Rock river. In general, the diggings are more frequent and more extensive towards the west, and become more detached and lighter towards the east, but with some important exceptions. These will be noticed, hereafter, more in detail. STRATIFICATION. The rocks, in this district, form a series of strata, overlying each other nearly horizontally, already noticed in preceding reports. In describing them, I shall point out such characters and distinctions as I have myself observed, and which have appeared of practical importance. It has been noticed in other mining countries, that different rocks have different relations to particular minerals; that a given metallic vein, in one stratum, will yield more abundantly than in another, and will present peculiar characters in traversing each stratum. Such appears to be the case in this mineral district, and it hence becomes important to mark, as far as possible, all the different modifications in the strata. The surface of the mineral district may be regarded in general as a plain, traversed in different directions by valleys and ravines, radiating from the principal water-courses. Seen from a distance, these are less obvious, the higher points of the surface, themselves on nearly a common level, commanding the view, and giving to the whole the appearance of a vast plain. Above this plain rise a number of elevations, called mounds; some isolated, such as the Blue Mounds, the Platte Mounds, and the Sinsinawa Mound, in Wisconsin, and others forming connected chains of highlands, such as the range east of Galena, in Illinois, and the. Highlands along the west side of the Mississippi, in Iowa. These mounds are composed of strata, overlying the strata occupying the general plain. The strata, in this district, appear nearly horizontal, but have slight dips in different directions. A general dip to the west of south has been recognized in former reports. A general dip to the south appears obvious, even if the part of the district examined by me be alone considered. Such a dip to the south would, in a general plane surface, bring the lower strata to that surface successively towards the north, and such, in the whole, appears to be the fact in this district. A general dip to the west has appeared to me less obvious, though favored by many facts, particularly the great extent of the mound rocks in the Highlands of Iowa, and the greater thickness of the upper strata generally towards the west. Besides this general dip, local inequalities in the stratifica tion may be observed at various points, indicating extraordinary elevations of the strata at those points. These appear to be rather detached elevations at different centres, than along extended lines of anticlinal axes. They occur generally in connexión with the deeper valleys, where there has been a considerable degree of denudation, and at such points the lower strata are brought to the surface at extraordinary elevations, and exhibit striking inequalities within short distances. Such points of elevation may be observed on Fever (Galena) river, between Benton and Shullsburg; on the West Pecatonica, near Mineral Point; on the East Pecatonica, near Argyle; on the waters of Sugar river, near the line of Dane and Green counties, and on the Platto river, between Platte ville and Potosi. From these centres of elevation the strata dip in different directions, by which the higher strata are found successively overlying the lower on the north as well as on the south, Thus the extraordinary dip to the north from the centre of elevation on Fever river presents the overlying strata on the surface to the north of the outcrop of the lower strata, and has given place for the occurrence of the mound strata at the Platte Mounds. In the same manner, there is at Dodgeville, though six to seven miles north of Mineral Point, a greater thickness of strata than at the latter, near which the lower magnesian is even brought to view:The details respecting these elevations will be given after the description of the different strata. The series of strata, which I have had an opportunity of examining, may be thus arranged. 1. The Mound Strata, consisting of three distinct beds of limestone; the upper, middle and lower. 2. A bed of Blue Shale, separating the mound strata from the next lower limestone series. 3. The Upper Magnesian of Owen, also consisting of three distinct beds. 4. The Blue Limestone, including the Blue and the Buff Limestones of Owen (1st Rep.,) also presenting three distinct beds. 5. The Upper Sandstone. 6. The Lower Magnesian of Owen. This last I have not yet had an opportunity of examining through its whole depth, but I have observed, in its upper portion, two distinct beds, well characterized. 7. The Lower Sandstone. This I have not yet had an opportunity of examining in connexion. The arrangement of each of the limestone se ries, at least of the three upper, in three distinct beds, is worthy of attention. Other minor distinctions may be noticed, and have in different places attracted the attention of miners, as of practical importance. These I have endeavored to ascertain, and shall men. tion, so far as I have been able to determine them; but from their nature, they can be fully determined only by a more complete survey than I have yet made. MOUND STRATA. The Mound Strata, within the limits of the mineral district in Wisconsin, occupy only a few detached points, considerably ele vated above the general surface. These are: the Sinsinawa Monnd, a detached summit near the south line of the State and on the limit of the towns of Hazel Green and Jamestown; the Platte Mounds, two detached summits, one east, the other west of Belmont, with a smaller elevation of the same character between them; the Blue Mounds, two summits forming part of a connected range, near the line of Dane and Iowa counties; and the northeast point of a range of mounds, extending from near Galena towards Shullsburg. The three distinct beds, above mentioned, are most complete in the southern mounds, and are apparently partly denuded in the northern. They may all be distinguished in the Sinsinawa Mound, but the upper appears there less complete than in the Table Mound, an outlier of the Highlands, south-west of Dubuque. The entire series is composed chiefly of a thick-bedded limestone, finegrained and nearly white, when unstained, and well adapted for building. The upper bed is characterized by a great abundance of corals, of which the Catenipora is the most distinctive. The middle bed abounds more or less in hornstone (flint,) arranged conformably to the stratification. This, in the southern mounds, is less abundant, and more in detached nodules, while in the northern mounds, it is more abundant, and even, in the Blue Mounds, almost replaces the limestone. In the northern mounds particularly, it is distinguished by a reddish-brown colour. It may thus have given origin to the layer of red flint in clay, which immediately overlies the rock on the general surface throughout the mineral district. The lower bed contains little flint, and is less abundant in fossils, particularly corals, than the upper, It appears, however, thicker bedded, and is more important for lime and building. The mound limestone has never been found to contain any considerable deposit of lead ore. Traces of mineral are reported to have been found in it, and some fruitless excavations have been made, one of which I have examined on the top of the Sinsinawa Mound, but have observed there no appearance of lead ore. * C. escharoides. |