PREFACE. Though effort has been made in the following report to equably distribute credit for work done, it is proper to emphasize and call further attention here to the share of some in this publication. Thus, the geological mapping of the sheet is largely due to Mr. Haworth, who spent several seasons diligently outlining the areas of the crystalline rocks in this and the adjacent country; his work at the same time defined the general limits of the Paleozoic clastics, thus restricting further work on these rocks to the study of the sections and other details. To Messrs. Lonsdale and Marbut is due almost entirely the credit for the topography represented on the sheet; for, although begun under the writer's immediate direction, the topographic mapping was soon left to their independent charge. The idea prevailing in the other sheet reports of including exhaustive descriptive detail has had control here, and, thus, occurrences which have been noted in the Iron Ore report and other previous pub. lications have been rediscribed, though mostly in new form and with valuable additions; this repetition of publication is unavoidable in preparing all area reports. In the present instance, we feel that no apology is necessary for presenting Mr. Nason's new and excellent descriptions of Iron mountain and Pilot knob; the deposits there are of world-wide reputation and are most instructive geological illustrations; we can have little fear of placing on record too much detail concerning these unique object lessons; on the contrary, it is our duty to gather and preserve, while we are able, all facts of value which the progress of mining may reveal, so that they may be used for the guid ance and profit of those who come after us. The geographic position of the sheet was determined through the assistance of the U. S. Coast and Geodetic survey. Two points were determined, one at Ironton, and the other at Potosi, and the following are the results of the final computations: The station at Ironton was marked by a brick pier, and was located in a field about a hundred yards northeast of the railway depot. The pier at Potosi was of brick and stone and was located in the courthouse grounds. In addition to these points of control, the triangulation of the Mississippi River Commission was also used for properly adjusting the positions of the township and range lines. In the proof-reading of this report, Mr. J. D. Robertson has given much assistance, and the accompanying index was prepared by him. ARTHUR WINSLOW, State Geologist. JEFFERSON CITY Mo., Jan. 8, 1894. |