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POPULAR SCIENCE REVIEW. 
relations "with the existing flora of America, while the Cretaceous flora of 
Europe has more of an Indo- Australian character. 
The second report contains an account of the geological explorations in 
Wyoming Territory, preceded by a very interesting outline of the physical 
geography of the Missouri Valley and the sub-hydrographical basins 
connected with it. 
The third report comprises an account of the general geological, minera- 
logical, and agricultural characters of Colorado and New Mexico, made in 
a series of traverses across the districts in 1869, followed by two special 
reports on the mines and minerals and agriculture of Colorado. 
GEOLOGICAL SURVEY OF INDLANA.* 
T HIS volume contains the result of the survey made during the year 1869 
by the State geologist, Prof. E. T. Cox, assisted by Prof. Bradley and 
Drs. Raymond and Levette, but which has since been followed by the 
reports of the survey for the years 1870-72. It contains descriptions of 
Clay, Greene, Vermillion, and other counties, as well as investigations in 
Warren county, with a view of determining the character of the coal-beds on 
the northern limits of the Indiana coal-field. The area of the coal-measures 
is computed to approximate 6,500 square miles, or more than half as large 
as the entire coal area of Great Britain and Ireland. The Indiana measures 
form a portion of what is sometimes called the “ Great Illinois Coal-field,” 
which includes not only the coal area of Blinois, but that of Western 
Kentucky, Arkansas, Missouri, Iowa, Kansas, and Nebraska, from the facts 
that they were all considered as parts of one great basin. Taking a connected 
section of the coal-measures in Clay and Greene counties, the aggregate 
thickness is about twenty-eight feet of coal, including three seams of the 
celebrated “ Block Coal,” a name used by the miners to designate a variety of 
non-caking bituminons coal, for in coking it scarcely swells, and never cakes 
or runs together. It was first discovered on the western border of the Appa- 
lachian coal-field, where it is extensively used in blast-furnaces. It closely 
‘resembles in many respects the Scotch splint coal. It is free burning, and is 
remarkably free from sulphur ; the main seam is about four feet in thickness, 
and is traversed by two sets of vertical fissures, crossed at right angles, so as 
to allow the coal to be mined in large cubes or blocks — hence the probable 
origin of the name. With regard to the thickness of a coal seam as a means 
of identity over any great extent of country, Prof. Cox remarks, that it is 
only around the rim or margin of the western coal basin, and not throughout 
its central area, that we are to look for a succession of thick beds of coal. 
As we approach toward the central part of the basin, the coal-beds which 
surround it are either entirely absent or have dwindled down to seams that 
are only a few inches in thickness, their places being occupied by a pre- 
ponderance of argillaceous shale, some sandstone, and an occasional stratum 
* “ First Annual Report of the Geological Survey of Indiana.” By E. T. 
Cox. Indianopolis : 1869. 
