10 The American Geologist. July, 1896 
was probably the Permo-Carboniferous in tlie anthracite 
region of Pennsylvania shows that there is reason to suppose 
that the mass above the anthracite coal was heavier than that 
above the bituminous coal. 
8. On the supposition that this regional subsidence (pro- 
duced by the vast thickness of rocks) was profound enough 
and maintained long enough to allow the rocks to be atfected 
by this heat to such an extent or degree, as to materiall}' raise 
the temperature of tlie included water, then the combined 
actions of heated and compressed waters upon the compacted 
rocks, would produce change in the ])hysical and chemical 
conditions of the included coal beds. 
9. The coal, its pores being saturated with waters of its 
accumulation, thus subjected to hot water under pressure, 
would, in all probability, gradually undergo debituminization, 
and acquire a denser or more homogeneous texture. The 
natural inference is that the lower beds would be the most 
altered, just as the rocks of the deepest part of the subsided 
region would become most metamorphosed. 
10. A softening of strata means a weakening of it, and 
weakness leads to j'ielding or giving way. 
11. In order that our softened and thereby weakened Coal 
Measures might yield or give way, tlie only direction in which 
movement would be possible would be upwards or away from 
the se.at of metamorphism ; a bulging upwards might there- 
fore be expected to follow. 
12. Accompai^ying this upswelling of the rocks would l>e 
subaerial denundation, and in conjuction with the assumed 
lateral thrust given to the rising mass of rocks by the border- 
ing and perhaps now subsiding land, it seems proper to sup- 
pose that severe folding and rapid elevation into mountains 
would take place. Once the region began to rise, weakness 
would induce plication, plication and elevation would produce 
shrinkage, cracking, cooling, and extensive wearing away 
would accompany these processes. It is highly probable that 
mountain forming or the elevating process Avould go on much 
faster than removal by denudation or erosion. 
13. In the case of the Pennsylvania anthracite region it is 
supposed that the side-pressure on the uprising Coal Measures 
etc., was most severe or operated mainly from the east, thus 
