406 



DESCRIPTION 



in a geological and physical sense. Here is a mural face stretching several miles 

 each way along the shore of the Lake. 



One mile east of Tayhedah, by a rough measurement, I found the foot of the 

 perpendicular bluff to be one hundred and ten feet above Lake Winnebago, and its 

 upper crest one-hundred and forty-five feet, in the order represented in the annexed 

 section, taken one mile east of Tayhedah. 



Feet. 



1. Yellowish-gray limestone, ...... 16 



2. Light gray limestone, ...... 15 



3. Talus and slope, . . . . . . .110 



Total height of bluff, . . . . . .141 



Level of Lake Winnebago above Lake Michigan, . 160 to 16-1 



Beneath the bottom of the cliff, the rocks are not seen in place, being covered 

 by fragments, fallen from above, and by the red clay. The slope, from the clay up 

 to the cliff, is a mass of loose, jointed, cherty lime-rock, probably not very thick, 

 covering some softer beds of the same, only slightly visible, in a fragmentary state. 

 Above this is a compact, thick, coarse-bedded, light-gray lime-rock, 2, fifteen feet 

 thick. Next above this is a compact, coarse-bedded, yellowish-gray limestone, to the 

 general level of the country, sixteen feet. It is slightly fetid when broken, has reddish 

 spots, and thin, crooked cracks or seams, filled with a dry, ochery substance. In the 

 uppermost bed, there are small white siliceous spots, that stand out on the weathered 

 surfaces, which, on examination, prove to be fossils, tolerably well preserved, appa- 

 rently an Atrypa* and a coral like the Catenipora agglomerata (Hall), and some 

 small stems of Encrinites. The local dip is plainly northeast, and rapid. 



According to Captain Cram's report on the improvement of the Neenah or Fox 

 River, Lake Winnebago is one hundred and sixty-four feet above Lake Michigan ; 

 and by C. R. Alston, Esq., the present engineer, one hundred and sixty feet ; a 

 difference which arises from their giving the descent of the river, between the 

 rapids, by estimate merely. 



At two miles northerly, along the bluff where its foot is apparently about the 

 same elevation above the Lake, the dip is still very apparent, nearly in the same 

 direction as the last, that is, northeast by north. Here, the cliff is composed of a 

 compact, fine-grained, brittle, whitish-gray limestone, regularly bedded in smooth 

 layers, of eight to twenty inches thick, resting on a sandy marl. In this lime-rock 

 no fossils were visible, but in the marl immediately below, they were very nume- 

 rous, but so soft as to be scarcely recognisable after handling. This greenish marl 

 was almost entirely hidden by large blocks of the white lime-rock, and by a mass 

 of concrete limestone or tufa. One of the fossils appeared to be a Pterinea, very 

 indistinct. Another, the Orthis orbicularis, analogous to the species of Upper Lud- 

 low rocks of Murchison, or to Orthis striatula of the Trenton limestone ; a Cardium 

 striatum of the Aymestry limestone (Murchison). 



* The furrows on this small Atrypa arc deep, and perfectly smooth ; no stria, either longitudinal or 

 transverse. 



