of the Forest of Dean Coal-field. 199 



Along what may be called the Blakeney range of the old red, from Nevvn- 

 ham to Ailberton, the dip is from the river, or towards the Forest. 



A second dip, always gentle, but quite different, viz. towards the north-east, 

 is met with in the Ailberton Common ridge, also from Ailberton Chapel to 

 Bream Lodge, and in the lower strata belonging to the old red, which extend 

 nearly to Woolaston. 



This ridge of conglomerate is intersected, in one place, by a cross fault, 

 raising the part furthest from the Severn, and affecting the outline of the 

 limestone, but the dislocation cannot be traced into the body of that formation, 

 or far into the lower part of the old red. The line of hills, which may be 

 called the Chase Hills, from near Bream Lodge, by the east of Hewelsfield, to 

 Tidenham, have a third dip nearly parallel to the first. Each of these, where 

 it joins the next, seems generally to do so by a sudden line, not graduating 

 round ; but this is difficult to prove with certainty. The upper strata near 

 Bream Lodge are an exception, as they seem clearly to bend evenly round, 

 including the conglomerate at Prior's Meend. 



Carboniferous Limestone. 



The carboniferous limestone surrounds the Forest of Dean coal-field, with 

 the exception of the line of fault between Lydney Park and Denbigh Lodge, 

 a distance of four miles. According to Mr. Mushet, a bed of iron ore divides 

 the lower and more crystalline, from the upper and more argillaceous and 

 sandy strata. A section of these beds is well exposed on the side of the tram 

 road, about a mile below Cinderford Bridge, on the east side of the Forest, 

 and at Lidbrook on the north. 



There is a small outlier of the coal measures, including the lowest bed of 

 coal at Howl Hill ; it does not appear, however, to rest on the same bed of 

 limestone as that in the large field at Ruerdean, but on a more argillaceous 

 and thinner stratum, which is not supported by the bed of iron ore or lower 

 crystalline limestone. To the east both the limestone and the coal thin out, 

 or are cut off, the coal measures resting on the old red sandstone. The valley 

 of the Wye is cut through the limestone only, for on the summit of Copped 

 Wood Hill, the same argillaceous beds occur again, and all attempts to trace a 

 continuation of the outlier of coal, have been unsuccessful. 



On the Do ward Hill the iron ore bed reappears, and the ancient workings 

 on the summit of the Little Doward, may have been mistaken for an entrench- 

 ment, on that commanding and military position. 



The dip of the beds at Howl Hill is very slight, but it increases westwards 

 towards Doward Hill, where it is considerable. 



