STEVENSON— INTERRELATIONS OF THE FOSSIL FUELS. 203 



The carbon content of brown coal varies ; in a general way it 

 gives proof of great advance over peat, yet in many localities the 

 process of conversion stopped short of the stage reached by most 

 of the fuel peats of which analyses are available. Pliocene coal of 

 Bavaria has from 62 to 69 per cent. ; jMiocene coal from one mine 

 in Bavaria has but 49, the fideleny coal of Hungary has 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 

 'J2. The Oligocene coal in the Gran^Comorn district of Hungary 

 shows 65 to almost 74; the Brandenburg coals have 60 to almost 71, 

 the Zeitz area of Sachsen 64.78, and the Cologne area only 62. 

 Eocene coal of Bovey Tracey has almost 70; coal at Rockdale, 

 Texas, contains 67.36 to 77.11 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 and some reach 75, but in 

 Alaska coal from most of the beds has from 64 to 70. In Alaska 

 and Washington, there are localities where the carbon content is 

 much higher, but those do not concern the matter in hand, as there 

 is reason to look upon them as more or less metamorphosed. 



Beyond all question, there is at most localities distinct evidence 

 of progressive enrichment in carbon with loss of oxygen as one 

 descends in the scale. The extremes of carbon content in peat are 

 40 and 64 ; in the IVIiocene, 49 to 72 ; in the Oligocene, 58 and 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. 



