180 REPORT — 1856. 



steadily deepening and supporting more living inhabitants, it extended its bed as far 

 as the western side of Lake Michigan ; but not till the Scalent or Niagara age did 

 this second-time created palaeozoic ocean recover all its old domain. 



Break between the Middle and Lower Palceozoic Formations in the Anticlinal Zones of 

 Ohio, Kentucky, and Tennessee. 



The lower palseozoics rise to the day upon this wide flat wave in two districts ; 

 one enclosing Cincinnati, the other occupying a central position in the plain of 

 Middle Tennessee. Upon the Matinal strata, which are there very calcareous, 

 there rests not a vestige of the Levant or Medina formation, and scarcely a trace of 

 the Clinton or Surgent. The first Silurian deposit lapping upon the uppermost Cam- 

 brian, is the Scalent or Niagara limestone. Still more striking is the hiatus, where 

 the contact of the lower with the middle palaeozoic formations is exposed round 

 the margin of the Tennessee anticlinal, for there we find on its eastern side, neither 

 Levant, Surgent, Scalent, nor Premeridian rocks, that is to say, no proper Silurian 

 formation whatsoever, and on its western only a thin layer of the Scalent or Niagara. 



Break in Eastern Missouri. — From Lake Superior, by the valley of the Upper Missis- 

 sippi, and by the Ozark and Washita Hills, to the igneous range of the Rio-Colorado 

 of Texas, there is a chain of broad anticlinals, exposing ancient plutonic andgneissic 

 rocks, but chiefly the older paheozoics near their axes. Around every one of these, 

 either the middle, that is Silurian and Devonian, or upper, namely the Carboniferous 

 deposits, rest in discordant superposition with or without parallelism upon thePrimal, 

 Auroral, or Matinal members of the older palaeozoic division. This condition prevails 

 in southern Wisconsin, but to a more marked degree around the anticlinal area 

 traversed by the Missouri River eastward of the Osage*. 



On the western and northern borders of the Matinal area, some one of the Carbo- 

 niferous formations very generally reposes unconformably upon the strata of the 

 older palaeozoic or Cambrian age, all the middle formations, Silurian and Devonian, 

 being absent. Here then we have the clearest demonstration, that the anticlinal zone 

 of the Lower Missouri remained in the condition of dry land from the period of the 

 general movement of the bed of the Appalachian Sea at the close of theMatinal period 

 throughout all tlie long ages of the middle palaeozoic formations. This district gives 

 evidence of a similar, but less extensive paroxysmal movement, resulting in discordant 

 stratification at the beginning of the Carboniferous period, but the discussion of this 

 and other subsequent displacements of the crust can only be alluded to in this abstract. 

 The physical break visible throughout this western chain of anticlinals implies a 

 wider interval of time, or longer cessation of formative actions, than is discernible 

 anywhere further east within the Appalachian area. 



Reasoning from the data afforded by recent geological researches, especially those 

 of Owen, Norwood and Swallow, the author infers that the Silurian waters, even as 

 late as the Scalent or Niagara period, when they had attained their widest expansion, 

 were by no means co-extensive with the wide bounds of that earlier Appalachian 

 ocean which covered the Matinal and other primordial palaeozoic sediments. In the 

 middle latitudes of the United States, tjiis Silurian sea had crept no further eastward 

 than a line joining the Tennessee anticlinal and the Helderbexg Hills of New York, 

 prolonged thence into New England, Lower Canada, and New Brunswick. It occu- 

 pied the area of the present Laurentian Lakes, but did not reach the limit of the 

 ancient Matinal sea even in that direction, and towards the west and south-west it 

 did not spread to the Lower Missouri. It was merely a wide Mediterranean, covering 

 the area which is now the northern-middle and north-western Atlantic States. [Want 

 of space compels the omission of that part of the memoir which relates to the Sas- 

 katchewan palaeozoic basin, and to the Chippewayan region, or that west of the 

 Rocky Mountains.] 



Palceozoic Basin of Hudson Bay. — The north-eastern palaeozoic basin of North 

 America is encircled on three sides by a low, broad zone of gneissic and azoic strata, 

 between 200 and 300 miles broad, and of a curved length of not less than 3000 miles, 

 from Labrador to the Arctic Sea. This belt is not, in the proper sense, an axis of 

 crust elevation, but more truly, the still uncovered remnant of the broad floor of 

 metamorphic strata upon which the palaeozoic deposits of the two great basins which 

 * See Owen's Geological Survey and Map, of Wisconsin, &c. 



