1889.] NATURAL SCIENCES OF PHILADELPHIA. 285 



Muscatine county, fifty miles to the northward. But later investiga- 

 tions prove conclusively, as recently remarked by Calvin, x that 

 the strata last mentioned are Hamilton sandstones and therefore 

 not continuous with the beds of similar composition farther south- 

 ward. White, 2 following Hall, also considered the lower portion 

 of the Burlington section as Chemung, but afterwards 3 concurred 

 with Meek and Wort hen 4 that it was not Devonic, but belonged 

 properly to the age following. Thus after nearly twenty years, the 

 original opinion of Owen relating to the correlation in time of the 

 arenaceous beds below the " Encrinital " limestone in southeastern 

 Iowa is finally sustained. 



The Lower Carbonic rocks at Burlington have already been 

 treated in detail by Hall and White whose remarks in the present 

 connection will require but little supplementary explanation. Also, 

 recently, "' the leading topographical and cenological features of the 

 district under consideration have been briefly presented in a prelim- 

 inary statement. 



A generalized section of the depositions in the immediate vicinage 

 of the city exhibits : 



Loess ......... 



Drift (lower till) 



Upper Burlington limestone and cherts 



Lower Burlington limestone and siliceous shales 



Kinderhook: calcareous layers .... 



Sandstone ....... 



Limerock ....... 



Blue clayey and sandy shales — exposed 



250 feet. 

 It is to be noticed that the stratigraphic rocks of Burlington pre- 

 sent a maximum exposed thickness of nearly two hundred feet, a 

 little more than one half of which may be regarded as Kinderhook. 

 Lithologically the strata of the lower member are made up chiefly 

 of bluish sandy shales which in some places pass into fine-grained 

 sandstones. Towards the superior limit of this division are several 



1 Am. Geol., vol. Ill, p. 25. 



2 Jour. Boston Soc. Nat. Hist., vol. VIII, p. 209 et seq. 

 s Geol. Iowa, Vol. I, p. 191. 1870. 



* Am. Jour. Sci., vol. XXXII, p. 177. 1861. 



5 Keyes : Am. Naturalist, vol. XXII, p. 1049 et seq. 



