. Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean . three feet of arenaceous limestone ; and lastly, crowning the other forma-tions, calcareous rock of massive character, containing crystals of carbonate of Mr. Marcou mentions eight or ten great cones truncated at the summit, and from 60 to 100feet high. The strata are horizontal, and thick strata of red sandstone predominate,, withalternations of red shales more argillaceous and separating in thin leaves. Two or three bedsof a sil
. Reports of explorations and surveys, to ascertain the most practicable and economical route for a railroad from the Mississippi River to the Pacific Ocean . three feet of arenaceous limestone ; and lastly, crowning the other forma-tions, calcareous rock of massive character, containing crystals of carbonate of Mr. Marcou mentions eight or ten great cones truncated at the summit, and from 60 to 100feet high. The strata are horizontal, and thick strata of red sandstone predominate,, withalternations of red shales more argillaceous and separating in thin leaves. Two or three bedsof a siliceous limestone occur at the upper part, of a whitish grey color, very hard, and whichhas preserved the lower strata from denudation, forming natural mounds. This is a translationof Mr. Marcous description. 1 Simpsons report of the route from Fort Smith to Santa Fe, p. 8. 3 t 18 GEOLOGICAL REPORT THIRTY-FIFTH PARALLEL. A group of these remnants of a higher plain, forming a colonnade of sandstone so regularthat it seemed a work of art, was sketched by Mr. Mollhausen, and I present it as a fine exampleof the effects of degradation of horizontal COLUMNS OF SANDSTONE, SOUTH BANK OF THE CANADIAN RIVER. The geologist does not need to he informed of the origin of these singular mounds andcolumns of rock, hut as they are objects of wonder to many travellers and excite many fancifulspeculations, the following explanation is presented: These mounds were originally connectedtogether by a continuation of their horizontal strata so as to form a plain or table-land. Bythe action of streams and drainage water, deep ravines have been excavated in various direc-tions, and a large part of the plain has been washed away, leaving a remnant of the strata,the flat-topped mounds or columns here and there. Gypsum.—At Camp No. 30 a bed of white gypsum, twenty-five feet thick, was found in thebank of the creek. It rested on sandstone and shales, and above it a bed of dolomite was fo
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