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Download pdf Bulletins Volume 19

Download pdf Bulletins Volume 19

Bulletins Volume 19 by Geological And Natural Survey
Bulletins Volume 19
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Author: Geological And Natural Survey
Page Count: 102 pages
Published Date: 01 May 2012
Publisher: Rarebooksclub.com
Publication Country: Miami Fl, United States
Language: English
ISBN: 9781236142252
Download Link: Bulletins Volume 19
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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1907 Excerpt: ... the shale. At this horizon there is a firm, heavy layer of dolomite about 2 feet thick, known to the miners as the cap rock. Below it is usually another firm bed 8 to 9 inches thick, under which come certain thinner beds, which disintegrate easily and produce enlargements or openings where the formation is crossed by the crevices. These openings may be entirely clear or may be partially occupied by weathered dolomite or dolomite sand. The opening is ordinarily about 4 feet high; but by caving in of the roof and solution of the fragments chimneys are formed, which in places extend up to the overlying shale. This opening is not always found at the same horizon, but is generally present at or above the horizon indicated. The middle or second opening occurs in the heavy-bedded dolomite between the Receptaeulites zone and the flint beds. In West Dubuque it is ordinarily 40 to 50 feet below the cap rock of the top opening. The third opening is found about 26 feet below the cap of the second and is the one worked in manj-of the West Dubuque mines. It is a short distance above the flint beds as developed in this vicinity. In the top of the flint beds a fourth opening is sometimes found. Not all the openings are everywhere developed, though it is common to find two or even three in a single shaft. In cross section they do not differ much, and chimneys often extend from one to another. Pitches and flats have not been worked extensively in the Dubuque mines, though a north pitch was found in the Alpine mine leading down from the third opening, and Whitney a figures well-developed pitches in the Stewart and Bartlett mine at a level possibly higher. Working mines.--At the time of this survey comparatively little mining was being carried on at Dubuque. A little galena a...

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