S 
1893.] Recent Literature. 987 
As the conditions of deposition were evidently those of a slowly 
sinking sea shore, the marginal deposits or Lower Coal Measures prac- 
tically underlie the open sea formations or the Upper Coal Measures. 
Hence in the use of the terms Lower and Upper, though allowable in 
a general way, it must be remembered that along any particular plane 
the two series of deposits are contemporaneous and their separation 
therefore would be represented by an oblique rather than a horizontal 
plane. Under this view the author proposes to divide the Coal Measures 
or Pennsylvanian series into (1) the Des Moines stage, representing the 
marginal deposits, thus including all the coal, and (2) the Missouri stage 
representing the marine deposits. These correspond essentially with 
the Lower and Upper Coal Measures as ordinarily given. The coal 
seams are shown to have but a limited extent generally, and to be 
nearly worthless for correlation purposes. The seams vary from a few 
inches to seven or eight, and even ten feet in thickness, the average of 
the seams now worked being between four and five feet. They are not 
disposed in continuous layers over the whole area as commonly sup- 
posed, but in numerous lenticular masses from a few yards to several 
miles in extent. Being confined to the marginal areas they are asso- 
ciated principally with the sediments characterizing that class of depos- 
its, and have a sligbt seaward slope. They were laid down over an 
ancient eroded surface with hills and vales, ridges and gorges, and 
overlap Lower Carboniferous, Devonian, and even Silurian rocks. The 
paper is illustrated with numerous figures and diagrams showin 
graphically the structure of the Iowa coal field, and the essential dif- 
ferences between the views here advanced and those commonly held. 
Other papers of value are presented by S. W. Beyer, H. F. Barie 
and G. L. Houser. That of Mr. Beyer treats of an interesting discov- 
ery of eruptive rock in a deep well at Hull, Iowa, at a depth of seven 
hundred and fifty-five feet, interstratified with beds of sandstone con- 
stituting what was considered to be Sioux Quartzite. 
Additional facts bearing upon this occurrence of eruptive rocks in 
Iowa will be looked for with interest. 
As a whole the report shows marked wideness of taste and care in 
its makeup, though the proof reader evidently mislaid his glasses at 
certain points, or was it the typo who failed to note the corrections ? 
C HG 
Correlation Papers—The Newark System.'— This essay, pre- 
pared by Mr. I. C. Russell as a bulletin, is the sixth of the series of 
3 Bulletin of the United States Geological Survey, No. 85. Correlation Papers— 
The Newark System. By I. C. Russell, Washington, 1892. 
