FILLMOEE COUNTY. 291 



Trenton limestone.] 



sandstone becomes immediately white and friable, with a very slight cal- 

 careous cement. The Trenton plays the most important part in producing 

 the marked topographical characters of the central portions of Fillmore 

 county, since by its superposition over the crumbling St. Peter, it consti- 

 tutes the edge of the shoulder or terrace that marks their line of superpo- 

 sition, and not unfrequently spreads out on the top of an isolated table or 

 mound, thinly overlain by the lower layers of the green shale. Under the 

 head of surface features this point has been mentioned already, and the 

 reader is referred to that section. 



In Fillmore county the Lower Trenton, known sometimes as the "buff 

 limestone," which corresponds in horizontality with the limestone quarried 

 at Minneapolis and St. Paul, is much less affected by disseminated shale than 

 in those cities, and hence makes a much more desirable building stone. 

 The color is light blue, and in quarrying the layers rarely exceed five inches 

 in thickness. On weathered bluffs the bedding appears even thinner than 

 that, being apparently not more than two inches. When these layers are 

 opened and considerably quarried they combine, and produce layers that 

 are from four to six inches in thickness. They are generally tough and 

 hard, though when broken they often fracture conchoidally, and in unex- 

 pected directions. The most striking fossils are species of Orthoceras, often 

 regarded by the quarrymen as the remains of huge snakes, though really 

 oceanic shell-fishes, a beautiful species of Lingula, named Lingitla Elderi by 

 Mr. R. P. Whitfield, Orthis tricenaria, Con., 0. perveta, Con., Strophomena 

 alternata, Con., and numerous other brachiopods. 



The following details concerning this limestone will farther elucidate 

 this formation as it appears at various places in the county. 



S. E. J sec. 23, Spring Valley, quarry of John Kleckler. The rock here 

 is a gray limestone, with interlaminations of shale. This is very different 

 from the Devonian limestones, as seen at Spring Valley village. It is com- 

 pact, and, with the exception of the thin laminae of shale, consists entirely 

 of limestone. Exposed about ten feet. 



S. E. i sec. 23, Spring Valley, Jos. Lester has a quarry in the valley 

 of the middle branch, very similar to Kleckler's. That of Henry Prosser 

 occurs on S. E. J sec. 14. 



North part of sec. 25, Spring Valley. At Mr. H. Perkins' saw-mill the 



