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the Silurian is much broken up by faults. The great axial 
force being thus exerted so near the present outcroppings of 
the limestone is the primary cause of the very severe dip of 
the strata on the Eastern side of the district. The force of the 
upheaval on the Western side of the district seems to have 
been comparatively weak, unless, indeed, ultimately the rocks 
were depressed more on the Western than on the Eastern 
portion of the district. 
Near Bircham Grove Hill, a distance of a little over a 
quarter of a mile from the Carboniferous Limestone, and at the 
axial line of force, it is not elevated more than 1,600 feet above 
the present level of the Severn, but the top of the coal 
measures at this point was elevated about 4,300 feet above the 
_ same level. The Old Red Sandstone was also raised to a 
height of about 900 feet. The coal measures were 3,700 feet 
higher on the Eastern than they were on the Western side, 
and the Carboniferous Limestone was also elevated 3,400 feet 
higher on the former than on the latter side. 
About 14 miles West of the river Usk, the principal axial 
force which raised the Eastern outcropping of the Monmouth- 
shire coal field was apparently exerted, resulting in the up- 
heaval of the Carboniferous Limestone to a height of 10,000 
feet above the present level of the water in the Severn, but 
this main axial force was exerted at too great a distance from 
the Western outcroppings of the limestone in Dean Forest to 
affect it in a similar degree to that on the Eastern side. At 
the point referred to, West of the Usk river, the top of the 
coal measures must have been raised to a height of some 12,300 
feet; the Silurian itself was thrust up some 3,200 feet above 
the same line of reference. 
From this axial line, there has consequently been removed, 
by denuding and other influences, the astounding mass of 
material of 11,800ft. in thickness. This influence has extended 
along the line of country from the Monmouthshire coal-field 
towards the river Severn, and further to the East and South-East. 
The materials removed from the Eastern side of the Forest by 
similar agencies must have amounted to 7,500 ft. in thickness. 
