Sixteenth Annual Meeting. 19 



cretaceous; two others have so small a development that it is difficult to place them. 

 They are above the Niobrara, present some cretaceous appearances, but may possibly be 

 cither Lignitic (Laramie) or positively Eocene. The other two are Tertiary. The 

 modern alluvium is of course present in the valleys and ravines, and may be counted as 

 a seventh stratum. Beginning with the lowest, we will briefly describe each: 



No. 1. Is in its best development before weathering, a rather dark-bluish or lavender- 

 colored shale. It is in some places very friable and brittle, in others tougher, and passes 

 into a clay shale. Its color is much changed on exposure, becoming lighter, and in its 

 upper layers inclines to buff. It contains a large-sized inoceramus both in the Sappa, 

 Prairie Dog and Solomon outcrops, but we have only seen fragments. It has also numer- 

 ous fish scales and fin spines, and occasionally the vertebra and teeth. We have seen a 

 few saurian teeth, and have found in it the beaks of odontornithes — toothed birds — of at 

 least two species. As already indicated, this stratum outcrops in each of the main valleys 

 of the county, but in the Prairie Dog valley its upper layers lie low in the bed of the 

 creek, and it is from wells that we have obtained its best appearance. In the Sappa 

 valley it has a little more elevation, and in the Solomon valley it reaches from the river 

 bed to a height of about 30 feet above it. 



This blue shale passes gradually (and conformably) into the stratum above, which is 

 mostly a bright yellow chalk. The change from one to the other is so gradual in some 

 places, as to make it difficult to say where the line is. In other localities the line is so 

 definite that some slight irregularities suggest unconformability, but further examination 

 removes the idea. The greatest distinction we have observed is at two places, widely 

 separated. One, Miller's Spring, west of Lenora, where a fine stream of water comes from 

 under the chalk from the top of the shale; the other on the Sappa, where a depression 

 in the shale of a few feet across is followed by all the streaks of the chalk, which is here 

 beautifully banded. This little depression seemed to me just such a one as is often seen 

 on the seaside sands, where a little stream entering the ocean makes its little furrow in 

 the region between tide-marks. As it is to-day, so it was in the old Cretaceous sea. 



No. 2. We very soon gave this stratum the name of the Yellow Chalk. It is chalk, 

 and it is mostly yellow. We have seen since that Professor Cope has used the same des- 

 ignation for it, and this name will suit it well. It becomes in places in the southeast of 

 the county, and over in Rooks and other counties, white; but buff and yellow are the pre- 

 vailing tints. There are patches and layers of a brick-red and various shades of brown, 

 and, in bright sunlight, a rich orange. The play of colors in some outcrops is perfectly 

 gorgeous, particularly at Cedar gulch and Ghost creek, on the south side of the Solomon. 

 At the latter place the bold escarpments of the chalk lying over the shale, both in con- 

 tour and color, suggested a sunset by Claude Lorraine. At Norton Mill we were able to 

 measure the thickness of the chalk. It is there about 55 feet. On the Sappa it is nearly 

 as thick, but nowhere on the Solomon did we find it reach half that thickness, and in 

 the southern valley it nowhere reaches so low as the line of the water in the river bed. 

 It comes nearest to doing so at its most western outcrop, west of Lenora. This stratum 

 presents abundant evidence of metamorphism of rock by infiltration. It has had its 

 upper surface extensively covered by materials containing much silica, and through the 

 cracks and water-holes water charged with silicon has percolated, penetrated the porous 

 chalk, and changed it into various silicates, jasper, agate, and other forms. We have 

 seen a band of fine red chalk changed into a band of jasper, the yellow streak above still 

 rem a ining chalky. In crevices, ( as also in the shale below,) crystals of calcite and baryta 

 are found, and sometimes small crystals of quartz. In many of the occurrences of the 

 chalk the upper layers are altogether siliciiied. In one place, northwest from Norton, 

 these hard layers contain many cavities which are large enough for wells, and, contain- 

 ing much water, are so used. Many of the apertures through which water has entered 



