PLATE XL 



OLMSTED COUNTY, 1884. M. W. HARRINGTON. 



This county is quite similar to Fillmore in topography and all general features. 

 It has wide rocky valleys whose bluffs, however, are generally so rounded over by 

 drift and loam that they are not so precipitous as in Fillmore and Winona counties. 

 In general, further, the rocks at the surface are of the Silurian rather than of the 

 Upper Cambrian, and they therefore do not have that series of alternating sandstones 

 and limestones which facilitates the cutting of wide gorges by the rivers. In the area 

 of the Silurian, therefore, the gorges are inclined, in the absence of drift, to become 

 sharp and deep, but as they are largely drift-filled, they do not reveal themselves 

 until the drift and loam are re-excavated. Such old valleys are disclosed sometimes 

 by "sink-holes" which are formed by the collapsing of the loam, and which become 

 more frequent and larger in the direction toward the gorge of some creek tributary 

 to some of the larger streams. 



The towns of Rock Dell and High Forest are the most elevated of the county, 

 averaging about 1275 feet above sea mainly of prairie, while Orinoco and Cascade are 

 the lowest, being about 1075 feet above sea level, and more timbered. Originally 

 Olmsted county was well timbered. It has a characteristically loamy soil, but this 

 becomes sandy along the outcropping line of the St. Peter sandstone. There are no 

 lakes in the county, but numerous springs of pure cool water. These are by far the 

 most numerous on the south and west sides of bluffs where the natural dip of the 

 green clay of the Trenton causes the underground water to come to the surface as 

 springs, forming the "spring row " which characterizes many of the elevated plateaus 

 formed of the Trenton and the St. Peter. 



As in Winona, Fillmore and Houston counties, Olmstead county is furnished 

 with numerous small water powers at which feed -and flour making machinery is 

 kept in motion sufficient for the local demand, and at some of the larger water 

 powers extensive mills furnish flour for an extensive export. 



Many fossils have been collected from the Trenton in the vicinity of Rochester 

 and at Chatfield, and along the river at Stewartville. N. H. w. 



