GEOLOGICAL FORMATIONS. 685 



3. Beds of limestone three to four feet thick, containing but few flints; good build- Feet. 



ing stone 12 



4. Alternating layers of limestone and flints 9 



5. Beds of limestone 18 inches thick, separated by layers of flint two inches thick. . 19 



6. Heavy-bedded limestone, layers two feet thick, containing nuraerous intercalated 



flints, very hard and compact; stratification quite regular 17 



7. Very close-grained limestone, in beds about four feet thick; good for building 



stone; contains no flints 29 



8. Slope of the hill to water in the Mississippi river covering Galena limestone 91 



Total thickness 209 



The ground rises as it recedes from the bluff', so that there is prob- 

 ably an unexposed thickness of at least 40 feet of Galena limestone 

 above the top of the cliff. 



The Galena limestone is in many localities successfully quarried as 

 a building stone. This is chiefly the case in the southern and western 

 parts of the region, where the Buff limestone or St. Peters sandstone 

 cannot be obtained. The chief objection to it is the frequency of 

 cavities and soft places in it which render it difficult to dress, and 

 cause it to weather irregularly. For foundations, or any work where 

 beauty of finish is not the chief object, it is a good and durable stone. 



Paleontology. The organic remains of the Galena limestone are 

 quite abundant, but do not exist in such profusion as in the Blue 

 limestone. The characteristic fossil of the formation is the Recepta- 

 culites Oweni or lead coral, which is found indifferently in all parts 

 of the formation. Next in frequency are the Streptelasma (Petraia) 

 corniculum, and som 3 varieties of small Orthis. The most infrequent 

 is the Maclurea magna, which is found in the middle beds of the 

 formation. In the upper beds the Z,ingulaquadrata is quite frequent, 

 and often found in a fine state of preservation. Other and more in- 

 frequent fossils are the Pleurotomaria lenticularis, Belleroplion bil- 

 obatus, Orthis biforata, and occasional Orthocerata. 



CINCINNATI GROUP. 



Geographical Boundaries. This formation was found to cover a 

 much larger area of country than had previously been supposed. It 

 appears in T. 1, R. 2 E., and has an area of about five square miles, 

 contained in the following sections: 21, 22, 23, 24, 25, 26, 27, 28, 34, 

 35 and 36. In T. 1, R. 3 E., it is found in Sees. 30 and 31, covering 

 about one square mile. It does not occur north of T. 1, on ranges 2 

 and 3 E. 



Near the corner of Sees. 22, 23, 26 and 27, T. 1, R. 2 E., the forma- 

 tion attains an elevation of nearly 600 feet above Lake Michigan; and 



