THE LOWER SILURIAN ROCKS. 537 



of friable, entirely non-calcareous, sandstone, the summits far above 

 any apparently possible position of the Lower Magnesian, whilst be- 

 low their bases numerous other sandstone exposures occur, carrying 

 the sandrock down further. Nor are these occurrences of thick and 

 high-level sandstone at any considerable distances from points where 

 the regular succession of Lower Magnesian, Madison and Mendota is 

 to be observed. In places in the town of Westfield, on the western end 

 of the quartzite ranges, it is possible to pass within a quarter of a 

 mile from Mendota limestone, occupying its normal position, to sand- 

 stone ledges which rise from the same level for over 250 feet. 



As already described, the quartzite ranges almost completely en- 

 circle the intervening valley, whose altitude is somewhat greater than 

 that of the surrounding outside country. Within the valley, non- 

 calcareous, occasionally much-indurated, sandstone, with local con- 

 glomerate beds, is to be seen at almost all levels to the summits of 

 the quartzite ranges, but at two points limestone is known to occur. 

 These localities are described fully in a subsequent page. It is now 

 merely necessary to say that at one of tb.3 places, on the south flank 

 of the north quartzite range, near the Lower Narrows of the Baraboo, 

 are to be seen 20 feet of limestone, containing a number of fossils, 

 mostly of new species, which Mr. R. P. Whittield regards as unques- 

 tionably not lower than the Lower Magnesian. Below on the side- 

 hill are numerous but not continuous exposures of sandstone, those 

 nearest the limestone evidently forming the next lower layer, and re- 

 sembling closely the Madison beds. Across the valley, one-half mile 

 southeastward, is a vertical cliff of red-and-white-banded, fine-grained, 

 friable sandstone, rising from 75 to 165 feet above the summit of the 

 limestone, whose altitude is what would be expected for the Lower 

 Magnesian, from the occurrences of that formation a few miles to the 

 southward. One mile further west sandstone and bowlder-conglom- 

 erate, flanking the quartzite, rise similarly above the limestone. 



At the other point, not far from the village of Baraboo, and on the 

 north slope of the south quartzite range, exactly similar limestone is 

 found, without fossils, covering a small summit, and underlaid by ferru- 

 ginons, fine-grained sandstone, carrying Scolithus and Dicellocephalus 

 Minnesotensis. At a still lower level, near by, a fine-grained, yel- 

 lowish, aluminous limestone occurs, the three different layers having 

 just the characters and relative positions for the Lower Magnesian, Mad- 

 ison and Mendota beds. Below the lowest limestone layer, and within 

 a few rods of it, are, however, ledges of much indurated, non-cal- 

 careous rock, entirely unlike the friable dolomitic sandstone normally 

 occurring beneath the Mendota. Three miles south of east from here, 



