150 
communicated to this series. These beds of rock are affected 
in a similar manner as far Northward as Edgehill Iron Mine, 
but as we proceed still further North it has a diminished 
effect. Some portion of the Coleford Hill delf seam, worked 
in a colliery to the deep of Haywood Level Colliery, has been 
denuded seriously over limited areas; but the coal measures do 
not seem to have been affected by the contortions found in the 
limestone and Millstone Grit rocks at the St. Annals Iron 
Mine. These displacements must consequently have taken 
place long before the deposition of the coal seams. 
Curious phenomena exist in reference to the formation of 
the Forest of Dean coal seams, but a full discussion of the 
subject would require more space than can be devoted to it in 
this communication. The elements contained in my appended 
sections are of the greatest utility, interest, and importance 
both to the Mining Engineer and the Geologist. 
A comparison of these exhibits that a thinning-out of some 
of the intervening beds of rock and coal seams have occurred 
in various parts of the district, but such changes are, for the 
most part, local, and consequently confined to small areas. 
Sometimes the hard Argillaceous beds upon which grew the 
immense forests of trees and plants—from which the coal 
beds were formed—present sudden difference of level for 
limited distances, but in others they are less pronounced and 
more prolonged, causing a difference in the continuity of the 
thickness of some of the coal seams after they were deposited. 
Generally, such effects were produced by erosive action. 
At Lightmoor Colliery we see by the section that the 
Churchway Hill delf had a thickness of 2ft. 10in., and that 
from the Breadless to the Churchway seam the intervening 
rock is 35ft. in thickness; but the thickness of the same bed 
of rock, as exhibited in Mr Mushet’s section, or No. 4, is 60ft. 
At some of the collieries the Churchway seam is divided into 
two distinct beds of coal of about 2ft. 5in. each, with 36ft. of 
rock between them, but at others they are found to be almost 
in contact. 
