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AliT, V .’^Observation on the Mineralogy of Hdlkin Mountam^ 
in Flintshire ; with a 'particular account of the recently dis- 
covered Buhr stone and Porcelain- Clay of that place. By 
Thomas Stewaet Teaill, M. D. F. R. S. £. M. G. S., &c. 
In a Communication to Professor Jameson. 
The elevation known under the name of Halkin Mountain, 
is one of a range of hills, stretching from Holywell towards 
Mold, and has been long celebrated for the richness of its mi- 
neral veins. From these a prodigious mass of lead-ore has 
been extracted ; and there are at present extensive mines 
wrought in different parts of this ridge : but its mineral wealth, 
within the last three or four years, has received an important ad- 
dition from the discovery of a curious siliceous rock, admirably 
adapted to supply the place of the best French Buhrstone in 
our flour mills ; and of a bed of beautiful white Clay, which is 
now successfully employed in the Staffordshire Potteries. To 
render the account of these interesting substances more complete, 
I shall commence with a brief survey of the geological features 
of this part of North Wales. 
The district of Flintshire bordering on the estuary of the 
Dee, may be considered, in a general point of view, as formed 
of three nearly parallel ranges of hills, with the intervening 
valleys. The range which skirts the river is low, undulating, 
and, after some miles, sinks into a plain of considerable extent. 
The surface in this first portion of the district is covered by a 
fertile soil, presenting a beautiful intermixture of woods and cul- 
tivated fields. The soil rests on an extensive coal formation, in 
which the beds are clay, shale, sandstone-flag, and coal ; which 
last alternates with the other substances in twelve distinct beds 
of various thickness. The most ancient coal-mines in this for- 
mation are near Mostyn-Hall ; and som§ of them have been 
wrought since the time of Edward I. The mines have the 
depth of from 100 to 135 yards. In the principal mine at pre- 
sent wrought, the first coal-bed occurs at the depth of 33 yards, 
and is covered by clay, shale, and a thin sandstone-flag contain- 
ng much mica. The different beds of coal vary from 1 foot 
to 9 feet, and even 15 feet in thickness, and their general incli- 
nation is estimated at one yard in tliree ; varying from one in 
