144 
AGE CHARACTERISTICS OF COALS 
but 54; and the Grottauer coal in Bohemia has 53; but in other 
localities in Bavaria the carbon is almost 71; and near Brennberg, 
in Hungary, it is 72. Oligocene coal in the Gran-Comorn district 
in Hungary shows 65 to almost 74; the Brandenburg coals have 
60 to almost 71; the Zeitz area of Saxony 65, and the Cologne 
area only 62. Eocene coal of Bovey Tracey has almost 70; coal 
at Rockdale, Texas, contains 67 to 77 in samples from several 
mines on the same bed. In the northern areas within the United 
States there are few analyses showing less than 70, while some 
reach 75; but in Alaska coal from most of the beds has from 
64 to 70. 
Beyond all question there is at most localities distinct evidence 
of progressive enrichment in carbon, with loss of oxygen as one 
descends the scale. The extremes of carbon content in peat are 
40 to 64; in the Miocene, 49 to 72; in the Oligocene, 58 to 70; 
in the Eocene, 64 to 79. At the same time one must recognize that, 
as in peat deposits, the progress of change was checked in some 
localities at a much earlier stage than in others. 
Coal of Cretacic age occurs more or less abundantly in many 
countries. The original areas in which it was formed vary from 
mere patches to thousands, even hundreds of thousands of square 
miles; but these greater areas have been broken by erosion into 
isolated basins, or into isolated fields, sometimes widely separated. 
The coal seams are not confined to a single horizon, but are 
present throughout the Cretacic section at localities where proper 
conditions existed. The several regions have so many features 
in common as well as so many in contrast that a detailed descrip¬ 
tion of some typical areas, though perhaps tedious, is almost nec¬ 
essary for proper understanding of the relations. 
Cretacic deposits are present on the Atlantic and north Gulf 
coasts of the United States, but they contain no coal; and the 
occurrences of lignite have interest only for the paleobotanist. 
The important area is in the west-central region, where the de¬ 
posits originally extended from the 95th meridian westward for 
not far from 1000 miles, and from latitude 25 degrees north in 
Mexico northward for not less than 2100 miles; in all not less 
than 2,000,000 square miles. These figures are merely approxi¬ 
mations ; and the area of greatest expanse may have been consider¬ 
ably larger. The continuity of these deposits was destroyed by 
post-Cretacic erosion following the Rocky Mountain revolution. 
