CHAPTER II. 
FORMATION OF CEDAR, AND PART OF LOWER IOWA RIVER, BELONGING 
TO THE DEVONIAN PERIOD. 
SECTION I. 
ITS LITHOLOGICAL CHARACTER. 
Tue rocks reterable to this age, as they occur in Iowa, are mostly calcareous 
strata of great purity. Many of its beds are light-coloured limestones, of close tex- 
ture, and flat, conchoidal fracture, approaching in structure to some of the litho- 
graphic limestones of Europe. Other beds are limestones of similar texture, but 
rugged and concretionary viewed in mass; and often reticulated with thin veins of 
chert and sulphate of lime. 
Interstratified with these are beds, more schistose, of argillaceous and marly 
limestones. : 
These rocks of Iowa differ, therefore, essentially in their lithological character 
from the contemporaneous great sandstone deposits, which, in Scotland, flank the 
southern slope of the Grampians, and encompass that portion of the eastern and 
western coast which lies to the north of the Friths of Forth and Clyde, as well as 
the northern coast of Sutherland and Caithness; while in England they occupy, in 
Devonshire, so large an area, as to have derived their usual appellation from that 
county, for the name of Devonian rocks now usually displaces that, formerly em- 
ployed, of Old Red Sandstone. 
far as this formation is exposed in lowa, no true sandstones have been ob- 
served in it,* not even of, a few inches in thickness; while, in Great Britain, red 
sandstones, highly charged with oxide of iron, make up the principal portion of the 
formation. 
The contrast in thickness in the two formations is equally remarkable. Nowhere 
in Iowa have I found an exposed connected section of these limestones measuring 
* The sandstones which sometimes lie in close proximity to the limestones here spoken of, appear to 
be of carboniferous date. 
