120 Trenton Limestone of Minneapolis and St. Paul — Hall. 



The Chemical Compositiok of the Layers. — Through the 

 kindness of Professor J. A. Dodge several analyses of these layers 

 of limestone have been secured. The following shows the compo- 

 sition of several samples with the results given in two tables, the 

 first with the soluble and insoluble portions analyzed separately, 

 and the second with both combined. 



Soluble and insoluble portions analyzed separately: 



COMPOSITION OF THE SOLUBLE PORTION. 



Silica SiOs 



Alumina AI2O3 



Iron Oxide FeaOs 



Calcium Carbonate CaCOs 



Magnesium Carbonate MgCOs 



Potash K2O 



Soda NaaO 



IV 



0.07 



7.81 

 13.74** 

 28.16 

 11.18 



Silica SiOz 



Iron Oxide Fe/Ja 

 Alumina AI2O3 . . 



Lime CaO 



Magnesia MgO . . 

 Organic Matter . . 



IV 

 20.31 

 1.57 



18.96 

 0.70 



Total insoluble 12.81 



Total soluble and insoluble 



9.21 23.31 



41.54 



.66 98.95 96.85 102.50 



Soluble and Insoluble Combined. 



SiO, 



A1.03 



FeaO 



CaCOa 



CaO combined with SiOz 



MgC03 



MgO combined with SiOz 

 K2O 



Organic Matter , 

 Total.... 



20.38 

 26.77 

 15.31=* 



28.86 



11.18 



99.66 98.95 96.85 102.50 



*Fe203 and FeO calculated together. 



