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ANNUAL REPORT

ON THE

GEOLOGICAL SURVEY

OF THE

STATE OF WISCONSIN,

BY JAMES G. PERCIVAL

MADISON:
BERIAH BROWN, PRINTER,

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To His EXCELLENCY, Wu. A. BARSTOW,

Governor of the State of Wisconsin..! In presenting this report on the Geology of Wisconsin, it is proper that I should state the circumstances under which the materials for it have been collected. On receiving my commission as State Geologist (Aug. 12, 1854,) I proceeded, agreeably to your instructions, to examine the mineral district, included in the southwestern counties of the State. It was my intention, in this examination, to make a preliminary reconnoissance of the entire district, so as to enable me to present, in my first report, a general view of the arrangement, both as exhibited on the surface and in the interior. In previous examinations of the same kind, I had found the great advantage of such general views, in preparing for a more just appreciation of particular facts, and of their mutual relations. One of the most important objects of a Geological Survey, indeed the most important, is to determine the system of arrangement, ånd the principles connected therewith, which may serve as a guide through what would be otherwise an inextricable labyrinth. This cannot be done satisfactorily without a minute and thorough investigation of particulars, but this should be made throughout with a view to the entire arrangement, and for this purpose a preliminary reconnoissance is required. · Although I lost no time in pursuing this, object, yet I found it impossible to visit the entire district, this season, and November 23, I returned to Madison, and after a brief examination of the country between that place and

Janesville, in reference to the strata, I applied myself to the preparation of my report.

I have visited, during this season, all the considerable diggings. from the sonth line of the State to a line drawn from east to west, north of Cassville, Beetown, Potosi, Platteville, Mineral Point, Yellow Stone, and Exeter, and from the Mississippi to the east part of Green county. Some of the less important diggings, within these limits, may have escaped my notice, but I have endeavored to make such an examination of those I have visited, as my limited time would allow. I have also employed, in preparing this report, such facts as I had collected the former year, in the employment of the American Mining Company (N. Y.,) in exploring different localities in the same district, and particularly in examining the different strata, in reference to the probable descent of the mineral through them. On this point, of so much importance to the mining interest, I had then ascertained a series of facts, which seemed to prove that all the limestones, from the surface of the upper magnesian to a considerable depth, at least, in the lower magnesian, were good lead-bearing rocks. My researches, this year, have enabled me to add many convincing proofs to what I had before ascertained, the whole showing a regular descent of the mineral through all the rocks, within the limits above indicated, except the upper sandstone. I have had no opportunity, this seaBon, of extending my researches in the lower magnesian, its outcrop occurring chiefly in the northern part of the district, which I have not yet visited. I had, the former year, also applied myself to the investigation of other points of much economical interest, and have made them, this season, leading objects in my survey. Such are the surface arrangement of the ranges, by which they are combined into different groups, which are themselves also arranged in connected series, showing a regular system of arrangenent, apparently pervading the whole district, so far as I have yet examined it; the vein character of the different deposits of mineral, recognizable in all their varied modifications; and the different character of the openings in the different limestone strata, show.

ing that while all of these are lead-bearing, yet that each presents some peculiarities in the arrangement and character of its mineral deposits. The facts, which I have thus far collected, on these points, appear not a little encouraging, as exhibiting regularity and order in arrangement, and striking analogies to the best mines in corresponding situations in Europe. The opportunities for examiaing the interior of mines, are not now as frequent as I could have wished, but I have improped every opportunity which has presented, and have been able, during the two seasons, to examine the interior of more than two hundred different mines, of varied extent from the smallest to the greatest.

From the short time that I have been employed by the State, it cannot be expected that I should prepare a complete report. La this, I have bad in view the immediate interests of the mineral district, and I have endeavored to give it a practical bearing. My object has been to give general views of more immediate importance, and rather to point out the method I design to pursue than to give the results of a survey. Local details, and such as have no direct bearing on my present object, are reserved to another occasion.

I have confined myself, in preparing this report, chiefly to my own observations, and have proceeded no farther than the facts, which I have myself collected, would seem to warrant. Although I have not yet been able to explore the whole mineral district, and may therefore have failed to ascertain some facts, which may have an important bearing in determining the entire arrangement, yet I have felt warranted, from what I have already ascertained, in stating, with some confidence, the conclusions to which I have already alluded.

The mineral district is of such relative extent; its resources, mineral and agricultural, are so great, that whatever interests that must largely interest the whole State. The act, making the appropriation for this survey, requires that that district should be first surveyed; but occasional opportunities may, in the meanwhile, be taken to examine such other points as may be of immediate im

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