172 GEOLOGY. 



the west on the east, north and northeast. These lands were partial- 

 ly the upraised carboniferous sea bottoms. As elsewhere, the pro- 

 gress of elevation left the latter Permian here without any memorials 

 of its existence. 



It is possible that in some section of the old world, not yet geo- 

 logically explored, remnants of this as }~et lost interval will be re- 

 covered or discovered. If so, we will no longer be compelled as 

 now to people this age with the changing life that then must have 

 existed. The old notion of cataclysmic changes of sufficient force 

 to destroy all life, and subsequently entirely new creations has long 

 since been abandoned. "Nature rarely turns a sharp corner." 

 Life has not ceased on the globe since it began. In obedience to 

 new conditions it has ever been changing into new forms. And in 

 no period of world history have the transformations been so great 

 as during the Permian Age. 



Character of the Permian Rocks. — Near and around Beatrice 

 there are many exposures of yellowish, occasionally bluish magne- 

 sian limestone, full of geode cavities lined with cale spar.* This 

 rock is arranged in layers from four inches to two feet thick; and 

 the whole series of strata are from twelve to twenty feet thick. 

 Below this there is a bed of yellow compact limestone from eighteen 

 inches to three feet thick. Next below, there is a thickness of from 

 eight to twelve feet of a dark grayish clayey limestone, also full of 

 geode cavities, lined with crystals of cale spar, and sometimes of 

 silica or silicate of lime. This stratum often becomes light colored 

 on exposure to the air. Occasionally it becomes massive cream 

 colored limestone. Wherever, therefore, such beds as thus de- 

 scribed are found in Nebraska, bordering the Upper Carboniferous 

 rocks, they invariably indicate our Permian deposits. Towards the 

 east, in Pawnee County, they runout, as the carboniferous then be- 

 comes the surface rock, which, on the contrary, in a westward 

 direction, run under the Permian. Above the first of these Per- 

 mian rocks there is a bed of variegated clay, and sometimes of pot- 

 ter's clay, whose geological age is uncertain, but which probably 

 belongs to the Dakota Group of Cretaceous rocks, which comes in 

 next above. This Dakota Group, itself, can be recognized by its 

 dark gray, brownish and red sandstones, which around and west- 

 ward from Beatrice overlies the Permian. 



*Ttaese geode cavities are now generally believed to be formed by cavities left in the 

 original sediments by covered up pponges, that subsequently decayed. 



