ORIGIN OF THE PENNSYLVANIA ANTHRACITE. 68 1 



produce by contact the extensive tracts of anthracite still 

 remaining in the state. 



Professor Rogers's explanation seems to have been based 

 throughout on a misunderstanding of the conditions. There is 

 no good reason for supposing that the Appalachian Revolution 

 was produced by violent disturbances such as those imagined 

 by Professor Rogers ; on the contrary, there appear to be the 

 best of reasons for supposing the final folding to be but an 

 acceleration of the process which had gone on, perhaps not con- 

 tinuously, from a very early period. The slowness of the pro- 

 cess even at the close is suggested by the courses of the main 

 waterways. The fundamental error, however, respects the rela- 

 tion of dip and volatile. The dip along the line selected by 

 Professor Rogers, that from Pittsburgh to the Cumberland coal 

 field in Maryland, does indeed show great changes, but as already 

 stated they are not gradual. Let the condition be recalled. At 

 Pittsburgh, the dip is from ^° to i° ; in the Coke basin, 30 miles 

 away, it is from 4°-6° at the lower portion of the trough, to 

 I0°-I2° higher up the side of the anticline ; in the Salisbury basin, 

 34 miles further, the dip is the same or less, there being practi- 

 cally no change in the interval from the Coke basin ; and no 

 further change is found until one has passed the Alleghanies and 

 entered the Anthracite Strip, where a marvelous change is seen, 

 for the dip is sometimes vertical. Now despite all this, the 

 decrease in volatile, as shown by the Pittsburgh coal bed along 

 this line, is almost regular; thus at Pittsburgh, the average 

 analysis shows of volatile 40.7 per cent, (ash and water being 

 ignored in the calculation); at Connellsville, 33.8, a decrease of 

 6.9 in 30 miles with an increase of dip from i° to say 8° ; at Salis- 

 bury, the volatile is only 23.3, a decrease in 34 miles of 10. 5 

 with no change whatever in rate or type of folding ; while in 

 the Cumberland basin, about 1 5 miles further, the volatile is 

 18.8, a decrease of only 4.5, despite the complete change in type 

 and remarkable increase in extent of disturbance ; and this last 

 field is within the anthracite strip itself, is in proper position, along 

 the trend, to be the continuation of the Northern Anthracite field. 



