BEE PLANTS OF CLAYTON COUNTY 
111 
source* The St. Peter sandstone gives rise to small springs while 
the larger ones have their source in the Prairie-du-Chien and the 
Galena-Platteville limestones (Fig. 15). 
Bdaphic and Floral Features.-— Where these alternatingly per- 
vious strata of limestone and sandstone and less pervious strata 
Fig. 15. One of a group of seven springs. Bluffs near Clayton, Iowa. 
of shale lie parallel are ideal conditions for the formation of 
springs, which are numerous on every hand, some being the sources 
of vigorous little streams. The soil includes both pulverized 
limestone and sandstone in quantities and is abundantly supplied 
with moisture. Sandstone derivatives include small quantities 
of compounds of silicon, aluminum, iron, magnesium, calcium, 
sodium and potassium while limestones include principally com- 
