166 Bibliographical Notices. 
(G. White), and Mississippi (B. L. Wailes); that Arkansas has been 
reported on by the late eminent geologist, D, D. Owen (1857-60); 
Texas is under examination by B. F. Shumard, and Illinois by A. H. 
Worthen; and that the geological constitution of the Western Terri- 
tories of the United States has been learnt chiefly by means of the 
Various expeditions, exploring, surveying, and military, undertaken 
since 1840. , 
- Few of the State-surveys, except those of New York and Penn- 
sylvania, rival in their results that of Iowa, whether we look to the 
elucidation of the geology of the country in letterpress, sections, and 
map, to the description and figuring of the characteristic fossils, 
or to the style and preparation of the books themselves. 
_ We have, however, only the first portion of the Report before us; 
and that is divided into two large volumes,—one devoted to the de- 
Scriptive geology, and the other to the paleontology, chiefly of the 
eastern counties of the State of Iowa. Messrs. Hall and Whitney 
were assisted by Messrs. A. H. Worthen, B. J. Hall, E. H rford, 
and E. A. Cooley in their geological explorations. They describe 
the country as being composed of nearly horizontal strata, of Paleeo- 
zoic age, often covered by heavy drift-deposits of clay, sand, and 
gravel. The strata have a N.W.-S.E. strike, and dip gently, with 
undulations, to the N.E. The lowest rock is the Potsdam Sandstone 
(500 feet seen), exposed in the valley of the Upper Mississippi and 
its branches, especially the Upper Iowa River: above this follow the 
Calciferous Sandstone, or Lower Magnesian Limestone of D: D. Owen 
(200 feet thick) ; the St. Peter’s Sandstone of D. D. Owen (80 feet); 
Trenton Limestone (100 feet), including the Black-river and Birds- 
eye Limestones ; Galena-limestone (250 feet) ; Hudson-river Shales 
and Limestones (100 feet) ; [the Medina sandstone and Clinton rocks 
seem to be wanting;| Niagara Limestone (150 feet); Leclaire Lime- 
stone (more than 500 feet); Onondaga-salt Limestones, &e. (180 feet); 
Helderberg (Upper) Limestones (more than 50 feet); Hamilton 
Shales and Shaly Limestones (60 feet) ; Chemung Shales and Sand- 
stones (80 feet): Carboniferous Limestones—Burlington Limestone 
(encrinital) ; Keokuk Limestone and Chert (Archimedal) ; Warsaw 
Limestone (Archimedal) ; St. Louis Limestone (coneretionary) ; [the 
Ferruginous Sandstone of Missouri and the Kaskasia Limestone of 
Illinois are wanting ;| lastly, the Coal-measures. _ ; 
The lowest of these rocks occur only in the northern part of the 
State; the Coal-measures occupy the central and southern portions ; 
and the whole series can be seen in section along the Mississippi by 
traversing the entire length of the State, 
The geological formations of Iowa are those which are found to 
the eastward in New York and Pennsylvania; but, with one or two 
exceptions (especially the Potsdam Sandstone), they gradually be- 
come thinner towards the west. Thus the Cambro-Silurian rocks, 
from the Potsdam Sandstone to the Niagara Limestone’ inclusive, 
which are from 8000 to 10,000 feet thick on the borders of New Eng- 
land, or along the Appalachian chain, have a thickness of only about 
1380 feet in Iowa, Fr 
