GEOLOGY OF SOUTHWESTERN IOWA. 381 



cemented in some cases into a stony mass by the lime of 

 the limy water which percolates from the higher surfaces 

 through the Bluff Deposit. These, although sometimes 

 quite firmly cemented, are practically worthless, and are 

 mentioned here from the fact only that some have supposed 

 them to be parts of regular ledges of stratified rocks. This 

 is not the case, because the cementing process has usually 

 extended only few feet inward from the surface. 



Wood is not in sufficient abundance in this county to 

 supply at once a population with fuel that its soil is capable 

 of supplying with food, but that soil may itself be made to 

 supply all desired quantities of fuel in the form of forest 

 trees within a few years after planting them. 



Some very good bricks are made from a mixture of the 

 Bluff and Drift materials in the vicinity of Council Bluffs; 

 but good brick clays are nowhere abundant in this county. 



