274 Was7nulh on ihe Pittsburg Coal 'Bed. 
clay and slack veins, according- to the terms of geologist 
Rogers and all authorities, are transverse and longitudinal faults, 
and although small in extent they prove beyond doubt that the 
coal beds and i-ock at the time of the disturbance from their 
original horizontal position, have been as hard as to-day, which 
will be explained in the following. 
The synclinals or "swamps" indicated in fig. i, dip very 
gently; sometimes their deepest point is hardly two feet below 
the corresponding point of the anticlinal. The shortest line be- 
tween two corresponding points of two anticlinals and through 
the corresponding point of the sjaiclinal is longer, as the short- 
est connection of the two points of the anticlinals; consequently 
if the coal and rock had been in a soft or plastic state at the 
time of the disturbance from their original position, in order to 
cover the greater length they must have been thinned out by 
the over-lying measures, either with or without more or less 
fracturing ; i. c. by upheaval the measures of the anticlinals must 
have been thinned out. The facts demonstrate, that the thick- 
ness and lamination of the coal and rock remain uniform all 
over such synclinals (i. e. anticlinals) and in order to cover the 
greater length the coal bed and country rock are disconnected 
as illustrated in fig. 2. By a great number 
of disconnections of the measures in the 
mine referred to, always the fracture of the 
roof rock is smooth and sometimes polished 
and with distinct striation, although irregu- 
lar in its course; and from these facts must be concluded, that 
the coal and rock have been hard at the time of the disturbance 
from their original horizontal position; that fracturing took 
place when the sinking of the measures commenced and that 
the disconnected hard measures by continued sinking rubbed 
on each other and the fracture widened out, thus producing the 
results described before. Had the rock been soft or plastic at 
the time of the disturbance no such smooth polished and striated 
planes could have been produced, because only hard substances 
smooth and polish each other by friction. The width of the 
fracture of the coal bed, fig. 2, differs from a few inches to two 
and three feet, and while the sinking has been so trifling the pro- 
jections of the fracture remained in their original shape, the 
