HYPOTHESIS OF TRANSFORMED MECHANICAL FORCE. 61 



Virginias ; yet there is no anthracite in southwest Virginia or along the 

 Kanawha river. On the contrary, the Imboden coal-bed, toward the 

 bottom of the lower coal group in Wise county, Virginia, has almost as 

 much volatile combustible as the Pittsburg coal-bed has at Pittsburg. 



There are instances within the anthracite strip which tempt one to say 

 that the decrease in volatile is in direction of decrease of cover. The 

 Lykens valley coals of the Southern anthracite field, which have as 

 much volatile as the Bernice coals at the extreme northern portion of 

 the first bituminous basin, belong not to the upper coal groups, but to 

 the Potts ville. 



An equally satisfactory illustration is found in the Arkansas field. 

 The upper coal division is about 3,000 feet thick and its important coal- 

 bed is near the bottom. The main coal of the lower coal division is at 

 about 750 feet lower in the column. The upper bed has a fuel ratio ot 

 6.15, while that from an opening in the lower bed, less than a mile aAvay, 

 has a fuel ratio of 7.30. That this difference cannot be explained as due 

 to the influence of additional pressure or of increased earth-heat because 

 of the column of 750 feet of rock is evident from the fact that the coal- 

 bed of the intermediate division is opened almost midway between the 

 two localities, and its coal has a fuel ratio of 4.97, much more volatile 

 than is contained in the upper bed. 



OBJECTIOXS TO HYPOTHESIS OF MECHANICAL FORCE TRANSFORMED INTO 



HE A T. 



MalleVs Investigations. — Mallet's investigations, showing the quantity 

 of heat evolved by the crushing of rock, have been a fruitful source of 

 hypotheses respecting metamorpliism. There is no room for doubt that 

 such crushing can produce heat ; tliat it might produce heat enough to 

 convert bituminous coal into anthracite; the difficulty is not in the con- 

 ception of possibility, but in finding evidence of probal)ility. The pre- 

 sumption in every case is against the supposition that the anthracite, 

 granting that it is the result of metamorphism, Avas metamor|)hosed by 

 heat due to this agency. The instances of metamorphism unequivocally 

 due to crushing and folding are none too numerous, whereas instances 

 in which no metamorphism has taken place despite the most violent 

 crushing are sufficiently numerous. 



Evidence of the Virginia Coals. — The Pocono coals in southwest Virginia 

 have been crushed during the folding and faulting of that region until 

 in some localities they are as flaky as pastry crust. The filmy layers 

 can be separated by the fingers, and their surfaces are polished by the 

 chafing which they have endured ; 3"et that coal is rarely more than 

 semi-anthracite, and in some localities it is a semi-bituminous coal. The 

 Pottsville coal at Quinnimont, West Virginia, is in the gently undulated 



