MISSOURI. 



157 



6. Down the St. Louis & Iron Mountain R. R. we have St. Louis limestone, then Warsaw 

 limestone, Keokuk limestone and Burlington limestone within 20 miles. Crossing the Merrimac 

 River, we find the last for a while, then the Receptaculite, Trenton and Black River limestone, 1st 

 Magnesian limestone, and at Horine Station the Saccharoidal sandstone, very soft, used for glass- 

 making, and is very white and pure. Afterwards we have 2d Magnesian limestone. Crossing Big 

 River, the 3d Maguesian limestone near Iron Mountain. De Lassus, Mine la Motte, Frederick- 

 town, Pilot Knob, Des Arc and Annapolis are porphyry hills of Huroniau age, and the adjacent 

 limestones and lower sandstones and conglomerates are probably Potsdam. At Mine la Motte and 

 Fredericktown are certainly Potsdam fossils, but the absolute line (if any) has not been determined 

 between the Potsdam and Calciferous beds. Near Iron Mountain, Knob Lick and Cornwall are 

 superior granite quarries, which may be of age of Laurentian. 



7. Polishing stone. 



