St. Peter s Sandstone. 



I 2 I 



who says that if this quantity of quartzose sand be the 

 result of the mechanical attrition of azoic rocks, that 

 it is difficult to understand the absence of detritus which 

 would come from the destruction of schistose, feldspathic and 

 trappean rocks which make up so large a portion of the azoic 

 series. "The uniform size of the grains of which the sand- 

 stone is composed, and the tendency to the development of 

 crystalline facets in them, are additional facts which suggest 

 the idea of chemical precipitation rather than of mechanical 

 accumulation." 



The later discovery of fossils, although in limited numbers, 

 has now caused it to be generally regarded as of mechanical 

 origin. Upon this point Prof. Chamberlin* says that " the 

 existence of the remains of marine life demonstrates that the 

 fossiliferous portions at least are submarine deposits, while 

 the well-rounded character of the grains, the ebb and flow 

 structure, the shaly laminations, the conglomeritic portions, 

 and its relations to the adjacent formations, leave no doubt 

 that it belongs to the common class of oceanic sand deposits." 



ECONOMIC VALUE. 



The purity of the sandstone and its peculiar character have 

 rendered it of value in the manufacture of glass in certain 

 localities. The fact of its being generally overlain by a. 

 heavy stratum of limestone, has given it even more value to 

 mankind, inasmuch as it is the cause of many waterfalls which 

 are utilized for manufacturing purposes. It is the cause, for 

 example, of St. Anthony's Falls, which has been to Minne- 

 apolis a source of immense wealth. Prof. N. H. Winchell, in 

 the first annual report of the Geological and Natural History 

 Survey of Minnesota for 1872 (1873), page 92, says, that at 

 present the "sandstone is not known to be used for any purpose 

 within the State except for mortar for the local markets and 

 as an engraving board for idle boys. Sometimes beer vaults 

 are made in it along the river bluffs, and sewers for the drain- 

 age of the cities of St. Paul and Minneapolis are excavated 

 through it, the overlying limestone affording a secure roof." 



*Geol. of Wisconsin. Vol. II, 1S78, p. 288. 



