From these considerations, it is reasonable to infer that many 
of the known rocks were originally superimposed, and it is not 
difficult to conceive how these were removed in succession down 
to the present level during the many changes which have occurred 
during past Geological epochs. 
The grand old historical Severn, with its varied but fertile 
valleys, is an interesting and graphic example of the final result 
of such active changes as were due to natural phenomena con- 
nected with the earth’s history. 
The Mineral Basin of the Forest of Dean is of an oval 
form, the narrowest part of which is situated near to Lydney. 
Nearly all the seams of coal contained in it are generally ina 
regular form, having their outcroppings pretty clearly defined, 
except at such places on the surface where sudden change of 
level and displacement by faults have more or less obliterated 
their continuity. The Trenchard seams are the deepest, and 
extend over the largest area, but whether others were formed 
below, we have, at present but little or no evidence. 
The Coleford Hill delf seam is more general in its con- 
tinuity, and more valuable than the Trenchard, but its out- 
croppings are within those of the latter, and consequently its 
area is somewhat less. All the other succeeding seams upwards 
have diminished areas until we arrive at the upper series, 
the Woorgreens. A cross section of these seams of coal, in- 
cluding the rocks, is very similar in appearance to a nest of 
irregular tea-saucers of various sizes and depths, fitted one into 
the other, the intervening spaces representing the beds of rock 
and shale which separate the seams. 
The iron-ore measures extend beyond the limits of the 
coal formation, and have been estimated to extend over 39 
square miles, or 25,000 acres, but another estimate made ‘by 
the same party makes it equal to 16,000 acres. 
The late Sir Warrington Smyth stated that the coal basin 
is about 34 square miles, or 21,760 acres. 
Some years since, the writer made an estimation, using 
one of the Government maps for the purpose, and found that 
the Coleford Hill delf seam of coal extended over an area of 
