124 Wisconsin Academy of Sciences, Arts, and Letters. 



stone, soft, porous, and in places, easily disintegrated coral form- 

 ations, termed bj Profs. Hall and Chamberlin, coral reefs, which 

 were formed on the top of sedimentary rocks, less than one hun- 

 dred feet deep, in an ancient sea. 



That these coral reefs extended from the south of Kewaunee, 

 Wisconsin, in a southerly direction, below Bridgport, Illinois; a 

 distance of more than two hundred miles, and westerly, to Le 

 Claire, Iowa. < 



That at certain points in Milwaukee, Waukesha, and Eacine, 

 these coral reefs became more prominent and formed, as termed 

 by Prof. J. Dana, atolls, bordering on lagoons, which upon the 

 receding of the ancient sea, formed the fiords vallies, now occu- 

 pied by the numerous rivers of Wisconsin. 



Subsequently in the vicinity or same direction of these fiord 

 vallies, glacial vallies were formed at frequent intervals for long 

 lines of granitic boulders, of the Arch can age are found, some 

 measuring many tons, in size and weight; they no doubt had 

 an agency in producing the grooveS; scratches and polished sur- 

 face, exhibited on the tops and sides of the ledges of the com- 

 pact and fine grained limestone. The compressed condition of the 

 fossils appears to be due to an upward pressure from an upheaval 

 at the era of Silurian eruption, from which the same cause may 

 have changed portions of the sedimentary dolomitic strata, 

 either hj igneous action or by solution into metamorphic beauti-. 

 ful calcite, or strontianite. Such a theory would account for 

 the extraordinary compressed condition of fossil Cephalopoda, 

 and other genera, and calcite crystals in the Waukesha lime- 

 stone, and at the quarries in Wauwatosa, Eacine and elsewhere 

 in the state. An equally plausible theory is, that by a grad- 

 ual submergence, or subsidence ; and also from erosion, by the 

 waves and currents of the ancient sea upon portions of the found- 

 ation or base of the coral reefs, certain parts were undermined, caus- 

 ing the superior portion of the rocks to tilt over and slide down 

 in huge blocks, which give the appearance, upon exposure by 

 quarrying, of an upheaval of the strata. Such causes, explain 

 somewhat, the deep vertical fissures and seams, which permeate 

 every portion of the Wauwatosa reefs, and this situation is taken 



