184 Professor H. D. Rogers, on the Geology and [Feb. 8, 



Apart from these general phenomena of gradation which belong 

 to the conditions under which the strata originated, there exist 

 other facts of transition, which also imply a declension westward, of 

 quite another class of forces than the productive ones. In the 

 Appalachian chain, all the eastern coal basins, and the eastern 

 margin of the great Appalachian field, give evidence of a crust meta- 

 morphism, affecting all the palaeozoic rocks, the degree of alteration 

 dependant on the nature of the stratum, and its situation, eastward 

 or westward, in this great undulated zone. The coal, of all rocks, 

 the most sensitive to raetamorphism from heat, presents invariably 

 among the eastern flexures of the Appalachians, where the crust 

 action has been greatest, the condition of a hard and flinty anthracite 

 with a jaspery or large conchoidal fracture ; further westward in the 

 same set of basins, the anthracite has a more cuboidal fracture, is 

 softer, and is even slightly gaseous. Entering the eastern border 

 of the great Appalachian bituminous coal-field, we everywhere find 

 the coal possessed of only half its full share of volatile or gaseous 

 matter ; and it is not until we reach the middle and western side of 

 this wide basin, that the coal is found fully bituminous, — in other 

 words, not until we pass beyond the last of the perceptible undula- 

 tions of the crust. Throughout all the flat fields of the Western 

 States, the coal invariably retains its original full amount of bitu- 

 minous or gaseous ingredients. 



Comparing the areas of the coal fields of other countries with 

 those of North America now indicated. Great Britain may be 

 estimated to contain about 5400 square miles, France 1000, and 

 Belgium 510 square miles. Rhenish Prussia — Saarbrook field — has 

 960 square miles, Westphalia 380, the Bohemian field, about 400 ; 

 that of Saxony, only 30 ; that of the Asturias, in Spain, probably 

 200 ; and that of Russia, scarcely 100 square miles. And as these 

 are the principal known coal-fields in Europe, the whole is thus seen 

 to possess less than 9000 square miles of productive coal measures. 

 Comparing the coal areas with the total areas of the respective 

 countries, the United States has one square mile of coal-field to each 

 15 square miles of its 3,000,000 miles of territory ; Great Britain 

 has one square mile to each 22 J of surface ; Belgium a like propor- 

 tion ; while France possesses only one square mile of coal-field to 

 every 200 miles of country. Assuming the total area of the pro- 

 ductive coal measures of the world at 220,000 square miles, and 

 accepting 20 feet as the average thickness of the available coal, the 

 entire quantity, if estimated as one lump, is equivalent to a cube of 

 very nearly 10 miles dimensions, or equivalent to a cake or plateau 

 of coal 100 miles square in its base, and 440 ft. high. 



The present annual product of the chief coal producing coun- 

 tries is as follows : — Great Britain extracted from her coal mines 

 last year — 1855 — the enormous quantity of 65,000,000 tons ; 

 the United States, between 8 and 9,000,000; Belgium, about 

 5,000,000 ; and France, 4,500,000. 



