I5ROADHEAD — WELL AT ST. LOUIS INSANE ASYLUM. 219 



The above Section with specimens would indicate the forma- 

 tions about as follows : 



THICK- 

 NESS. 



GEOLOGICAL FORMATION. 



40 



SO 



670 



93 

 421 



148 

 135 

 5i7 



82 

 83S 



98 

 '3S4 



54, 

 2S54 



ft. .Clays of "Bluff" 



Coal Measures 



Lower Carboniferous Rocks 



Chouteau Group 



jTrenton with Black River and Birdseje 



(First Magnesian Limestone 



Saccharoidal Sandstone 



Second Magnesian Limestone 



Second Sandstone 



Third Magnesian Limestone 



Third Sandstone 



Fourth Magnesian Limestone 



Potsdam Sandstone 



Mostly all Granite, the lower 40 ft. being certainly 

 I Granite ; the upper portion may be Sandstone . . 



TOTAL 

 DEPTH. 



I20 ft. 



79O 



883 

 I304 

 I4S2 

 I5S5 

 2I02 

 2IS4 

 302 2 

 3I20 

 3504 

 355S 



3S43* 



In the above section, the thickness of the several Geological 

 Formations is made up from Mr. Atkinson's descriptive sections 

 and an examination of specimens from the borings. It may there- 

 fore be considered only an approximation, for in a deep well, 

 where all material is brought up in a comminuted state, there 

 may be errors ; but from the data it as correct as we can make it. 



Two well-marked formations are recognized, viz., the red cal- 

 caieous beds at the upper portion of the Chouteau Group, and the 

 Saccharoidal Sandstone. They have formed the chief guides in 

 the construction of our section. An important fact is also brought 

 forth in the determination of thickness and extensive range of this 

 Sandstone, so useful for glass making, etc. 



For comparison, I give the following Tabular Statement of the 

 thickness of the same Geological Formations in different counties 

 of Missouri : 



