MINING. 107 
-of one part below the other. The strata containing mineral coal, inter- 
sected by faults, are generally of soft clay mixed with fragments of trap 
or porphyry. 
Pl. 23, jig. 4, shows a section of the rocks containing mineral coal in 
the region of Newcastle upon Tyne. The scale of the perpendicular is 
double that of the horizontal distance, so that in fact only half the dip is 
represented. The line 277 represents the great bed or seam of coal, which 
has a thick bed of sandstone for its roof. The Holywell shaft, to the left of 
the profile, the Carsdon shaft, a, the Algernon shaft, c, the Chirton shaft, d, 
the Percy shaft, ce, the Howdon shaft, and nine others, are cut through beds 
and seams parallel to each other. The part lying south from the River 
Tyne, g, below the morass of the Jarrow, 4, some hundred feet or more, is 
not represented, but may be estimated from what is shown in the section. 
The dotted lines and the roof of the bed or seam, 27, serve as the horizon 
to aid us in judging respecting the dislocations occasioned by the many 
faults which have destroyed the continuity of all the strata. In passing 
from the lowest southern point below the Jarrow morass, the roof of the 
seam or bed uprears itself at an angle of 10°, and is there interrupted by 
the first fault ; afterwards by the second, which raises it about twelve yards. 
A third fault meets the bed at p, which sinks it about thirty yards, whence 
the bed mounts at about the same angle up to c, where it is raised about 
eighty yards by the fault, so that merely the lower strata of the formation 
appear. Later it sinks again at B about 22 yards, and then passes on hori- 
zontally to a thick fault or dyke, a, which throws down the whole bed about 
280 yards, from whence it gradually rises again. 
Pl. 23, fig. 3, is a section of the coal strata of Ronchamp, a, in the 
department of the upper Saone. The distinctly marked seams are suddenly 
broken through by a porphyritic mass, s. In the plains of Champagne, 
lying beyond the interruption, there has been found a continuation of the 
red sandstone, c, which forms the roof of the bed of mineral coal, pp; Eis 
the transition slate, and at B we again find the porphyry. The boring works, 
66, and the shaft,.a, are carried down even to the porphyry, 8, but the bed 
of coal has not again been found. | 
A vem is a more or less thick mass of rock of proportionably small 
dimensions compared with the rock in which it is found, which differs in 
kind from the rock which incloses it, even when the inclosing rock and 
vein belong to the same species. We also apply in relation to veins the 
terms strike, dip, roof, and floor. Although the strata on both sides of a 
vein have the same successions, they are for the most part dislocated, and 
therefore do not form opposite continuations. Veins too have their disturb- 
ances and contortions, frequently more than beds, and are likewise often 
pierced through by other veins. 
1. Exprrimentrat Works. 
The existence of localities of beds or veins is' usually indicated by out- 
687 
