276 Wasimclh on the Pittsburg Coal (Bed. 
oped by the mine workings. It will be seen, that the strike 
line of the slack vein is somewhat parallel with the strike line 
of the measures. The fracture F or slack vein is about two 
inches wide and it is filled with disintegrated coal only, because 
the part of the coal bed on the foot wall of the fracture has slid 
down, or even both parts disproportionately, thus the projections 
of the fractured coal only have rubbed on each other and as the 
vertical dislocation is only about six inches, no disintegrated top 
rock could be dragged along. The measures on the foot wall 
of the fault are in a lower position than the measures on the 
hanging wall of the fault, which is the characteristic of "longi- 
tudinal faults" or "overlaps" and the "slack vein" referred to 
according to the terms of geologist Rogers is a "longitudinal 
fault " or overlap, or according to Heim, Koehler and other au- 
thorities, a "folding fault." 
The course of transverse faults mostly approaches the course 
of the incline of mineral deposits (lode-measures); the part of 
the deposit on the hanging wall of the fault has slid down, and 
is in a lower position than the part on the foot wall but, where 
the dislocation is trifliing and not distinct, mostly both parts of 
the coal bed have been slightly bent downwards on the fault. 
The courses of longitudinal faults mostly approach the course 
of the strike line of the measiu'es and the part on the hanging 
wall of the fault or fracture is in a higher position than the part 
of the measures on the foot-wall. 
The dip of transverse and longitudinal faults generally is 
greater than the incline of the deposits and measures, but in ore 
lodes, according to their origin, occur no longitudinal faults. 
It is a well-known fact, that clay veins, rather faults, of more 
or less extent, have been struck in a great number of mines on 
the Pittsburg coal bed. An investigation of several districts 
will prove also that the Pittsburg coal bed to a degree is de- 
vided into areas of more or less extent by erosion and clay veins, 
the latter crossing each other. Furthermore it is a well known 
fact that the filling of fractures and faults by clayish substance 
acts like a dyke against water and gas, demonstrated in coal min- 
ing in Europe and In the anthracite region. 
The Pittsburg coal measures are underlaid by the Devonian 
formation, or members of it, the reservoirs of oil and gas. It 
