Carboniferous Formation of Pennsylvania — Wasmuth. 315 
rubbed upon each other. Such faults are termed "longitudinal 
faults," or "over-laps," or "folding faults," (fig. 2). 
Faults, as described before, have been met with numerously 
in the Pittsburgh coal bed, but transverse faults there predomi- 
nate, perhaps on account of the general character of the gently 
plicated flexures of the most frequent and more or less deep 
synclinals. All fractures of the coal bed developed thus far 
run up high into the roof rock, and naturally the fracturing of 
^^ hard rock and coal produced uneven, rough 
'^^■°* planes; but the projections have disap- 
^^^*^*^'^ ^i* _^ peared entirely; the sinking of one part of 
the broken strata, or even disproportion- 
ate sinking of both parts produced friction; 
thus the planes of the fracture, although 
curved more or less, have rubbed each other smooth and 
polished (sometimes with distinct striation), and the bulgings 
of the fracture are filled with the disintegrated projections 
caused by fracturing. The different occurrences of faults show 
also that the fracturing of the strata took place Avhen its sink- 
ing commenced. 
Had the strata been in a plastic state at the time of the 
disturbance from their original horizontal position, no results 
as described before could have been originated,' for the enormous 
weight of overlying strata in connection with fracture would 
have produced a squeezing of the different substances into each 
other and the fractures would not be filled with disintegrated 
rock, sometimes pure clay; and therefore no such inversions as 
those constructed by some mining engineers and supposed by 
the second geological survey of Pennsylvania to occur in the 
anthracite measures exist; their existence is impossible, because 
the strata were hard at the time of the disturbance from their 
original position. 
The Pittsburgh coal bed, or rather the Carboniferous forma- 
tion, or even members of it, have been in a nearly horizontal 
position, and dislodgment of interior masses of the earth by 
volcanoes, etc., must have caused a greater or less sinking of 
parts of the earth's crust without any regularity, thus originat- 
ing a combination of synclinals and anticlinals of varying areas 
and depths. Parts of these anticlinals disappeared by erosion 
and thus we find the present synclinals of the coal bed more or 
