WINONA COUNTY. 255 



St. Lawrence limestone.] 



cretionary forces sprang up which produced segregations and crystalliza- 

 tions that are not found in the rest of the formation. 



The more regular beds of the St. Lawrence embrace a thickness gen- 

 erally of about one hundred feet. At Stockton the best quarry layers have 

 an aggregate thickness from thirty to fifty feet. The strata vary from six 

 to thirty-six inches in thickness. They ai - e extensively wrought at the 

 quarry of the Chicago and Northwestern railway between Stockton and 

 Lewiston, at Winona, and somewhat at Dresbach. The stone is light-buff, 

 generally somewhat vesicular, sometimes coarsely porous, and sometimes 

 compact and fine grained. For the quality of the building-stone the reader 

 is referred to a previous chapter where the dolomites and dolomitic lime- 

 stones of this formation are discussed. 



Below these massive layers, which constitute a part of the precipitous 

 bluffs of the county, there is a varying thickness of more fragile inde- 

 scribable rock, which can best be defined by Dr. Owen's term siliceo-argilla- 

 ceous dolomite, with occasional layers of an inch or two of crumbling white 

 sand. There is also a slow transition from the crumbling sandstone of the 

 St. Croix to the dolomitic firm rock of the St. Lawrence. In the first place 

 siliceous nodules elongated in the direction of the stratification, from a few 

 inches to several feet long, and from one inch to twenty inches thick, begin 

 to appear in the crumbling sand. In these nodules sometimes the individ- 

 ual grains of sand are discernible still, tightly embraced in the siliceous 

 rock which is nearly white on fracture and very hard. A few feet higher 

 in the strata these nodules, while increased so as to coalesce to the right 

 and left, forming nearly complete strata themselves, are seen to be softer, 

 and to embrace other matter besides silica. They are fine-grained and 

 show no rounded quartz grains; or such grains appear only in patches of 

 irregular distribution and form. At ten or fifteen feet higher the rock has 

 assumed that character which is almost indescribable, being greenish and 

 shaly and yet not a shale, calcareous and not a limestone, magnesian but 

 not a dolomite, finely siliceous but not a sandstone. This character con- 

 tinues through a thickness of forty to fifty feet of strata, and is like the 

 rock of the quarries at Hokah and Lake City. By degrees the siliceous and 

 aluminous components disappear from these strata, and they present the 

 finely compact structure of some of the building-stone layers, as seen in the 



