I3r Traill 07i the Mmeralogy of HaJkm Momitain. 
four to two in three yards. The general dip is towards the 
E. S. E. 
The Flintshire coal-beds extend in length from Llan-Asa^ 
through the parishes of Whiteford, Holywell, Flint, Northop, 
and Hawarden ; a distance, in a direct line, of about twenty 
miles Their breadth is limited, on the one hand, by the val- 
ley between the first and second ranges of hills, and on the other 
by the Dee. There can, however, be Mttle doubt, that the Nes^ 
'ton Collieries, on the opposite Cheshire shore, are part of the 
same coal-field. The Neston mines, indeed, extend nearly two 
miles under the bed of the river, in a direction towards Flint. 
Through this extent the coal beds are not to be considered as 
uninterrupted. They are subject to great irregularities from 
shifts and dislocations of the neighbouring strata, which in some 
places are so striking, that the coal-beds may be considered as 
included in a series of detached basins, of greater or less extent. 
An intelligent friend, practically acquainted with the coal-fields 
of this district, informs me, that near Northop, he has seen an 
instance of the coal-formation extending to the west of the val- 
ley, between the first and second range of hills ; and the same 
is said to occur near Holywell The cause, however, which gave 
the channel of the river its present form, seems to have produ- 
ced a dislocation of the coal-beds ; for the dip at Neston is said 
to be towards Wales, while that of the Flintshire mines is to- 
ward the opposite point of Cheshire. The coal of Flintshire is 
of various qualities. Some of the beds yield a coal in some 
measure resembling the candle- coal of Lancashire ; but most of 
it rather inferior to the best Wigan coal. Much of what I saw 
at Mostyn Goal- works was contaminated by pyrites. In this 
colliery, the main shaft at present only extends through nine 
beds ; the last of which is more than two yards in thickness, 
and rests on a bed of yellowish-grey shale, with a greasy lustre, 
in the numerous cracks which traverse it in all directions. This 
shale, which is three feet in thickness, is much prized for ma- 
king and setting of fire-bricks *f*. The refuse of some of the 
• The coat-fields which contain the great beds of ironstone smelted between 
Llangollen and Wrexham, in Denbighshire, are a continuation of the same coal- 
formation, 
•j* There are three other coal-beds below this shale, each from 3 feet to 3 feet 
'9 inches in thickness but a tremendous explosion of fire-damp, which took place 
