1 20 



Cincinnati Society of Natural History. 



In Missouri the " Saccharoidal sandstone" has been correla- 

 ted with the St. Peter's. It is known in several places along the 

 Mississippi River. There has been considerable dispute as to 

 the exact age of the Saccharoidal sandstone, but the latest 

 examination of it by Dr. F. L. Nason* led to the conclusion 

 that the division which has been made of first, or saccha- 

 roidal, second and third sandstones, and first, second, third 

 and fourth magnesian limestones can not be maintained. He 

 says the evidence is not sufficient to make more than, one 

 sandstone and one limestone formation. For the first he 

 proposed the name of Roubidoux sandstone, and for the 

 second the name of Gasconade limestone. It seems probable 

 that the strata that have been referred to the St. Peter's in 

 Missouri are Cambrain rather than Silurian. 



Finally, in Michigan, it apparently occurs in a narrow strip 

 running from the Menominee River to the Sault Ste. Marie, 

 the L,ake Superior sandstone having been considered by some 

 authors to belong to this period also. 



LITHOLOGICAL CHARACTERS. 



In all its typical outcrops the St. Peter's sandstone presents 

 the same characteristics, being a friable, coarse-grained sand- 

 stone, the grains cohering but slightly, except when per- 

 meated by carbonate of lime or various oxides of iron. It 

 then becomes hard and indurated. In color it varies greatly, 

 being white, red, brown, yellow, gray, pink, green, lilac, and 

 also being frequently banded in an irregular manner. It 

 occasionally shows stratification planes, and ebb and flow 

 structure, and rarely, ripple marks. In thickness it varies 

 from a thin layer to a stratum over two hundred feet thick, 

 though the latter is infrequent. Its peculiar character and 

 the supposed entire absence of organic remains have caused 

 it to be regarded by some authors as a chemical precipitate 

 rather than as of mechanical origin. We have already seen 

 that Keating, in 1824, considered it to be the former. The 

 same idea was advanced in 1858 by Prof. J. D. Whitney,!" 



*Geol. vSur. of Missouri, Vol. Ill, Dec, 1S92. 

 fGeological Sur. Iowa, Vol. I, Part 1, 1S5S, p. 341. 



