88 STEVENSON 



bed yields coal with the ratio of i :2.52, the same with that 

 from the upper bench of the bed east from Bernice.^ 



More remarkable are the differences existing in the benches 

 of the Mammoth coal bed within the anthracite region at the 

 Locust Spring and Indian Ridge colleries of the Philadelphia 

 and Reading company, as shown by the analysis of Doctor 

 C. M. Cresson, made for that company. At Indian Ridge the 

 extremes are 



Volatile matter 3.2 10.42 



Fixed carbon 96.8 89.58 



Fuel ratio i :30.2 i :8.6 



and at Locust Spring 



Volatile matter 1. 89 15. 3 



Fixed carbon 98.11 74.7 



Fuel ratio I : 52 l : 4.88 



Other benches show ratios between those quoted. In four 

 other colleries belonging to the same company, the differences 

 between the several benches are insip;nificant 



2 



i=>' 



The varying proportion of ash has no bearing upon the dif- 

 ference in volatile. At Advent bay, the upper bench has the 

 higher ash and lower volatile ; but near Bernice the high vola- 

 tile of the upper bench is associated with nearly five times as 

 much ash as is found in the lower bench ; at Locust Spring, 

 the bench richest in volatile is high in ash while another at 

 seven feet lower has almost the same ash but less than one 

 fourth of the volatile. Similar conditions exist at Indian Ridge. 

 Nor has the relative position of the benches any influence. At 

 Advent bay, the lower bench is the richer ; near Bernice, the 

 upper ; at Locust Spring, the highest bench of the mammoth is 

 the richest, while at Indian Ridge the highest volatile is 

 found midway in the bed. The difference in physical features 

 brings no explanation for coal in Virginia, analyzed by Mr. 

 McCreath and very closely resembling the top coal of Advent 



1 A. S. McCreath, Reports of Second Geol. Surv. Penn., MM. pp. 94-97. 

 Ann. Rep. for 1885, p. 318, GG, p. 214. 



2 Ann. Rep. Sec. Geol. Surv. Penn. for 1S85, p. 321. 



