248 Dr Traill 07i the Mineralogy of HaTkm Mountain^ 
old coal- works, by spontaneous decomposition, has been con» 
verted into a blackish clay, containing a small portion of sulphate 
of argil, and more sulphate of iron. Not far to the south of 
Mostyn-Hall, by the shore, is a singular cliff, composed of large 
masses of perfect slags, cementing fragments of semi-vitrified 
and indurated sandstone flag. Large blocks of this pseudo-vol- 
canic substance are scattered on the beach, and present a bril- 
liant contrast of colour, from bright fiery-red and orange-yellow, 
to pale lilac and dark iron-brown. These substances occur in 
two parts of the cliff. The most southern portion extends about 
20 yards in length. This is separated from the second by low 
cliffs of sandstone flag, about 110 yards long. The second, 
containing the most perfect vitrifications and scoria, extends 
about 25 yards. The whole cliff is from 30 to 50 feet high. 
The marks of fire in some places are only visible by the red co- 
lour and hardness of the shattered rock, while in others, the fu- 
sed matter has interlaced itself with the broken stone. The 
most perfect slags are detached masses, some of which are six or 
seven tons in weight. The whole is the product of an acciden- 
tal fire in a coal-work, extensive traces of which are still apparent 
above the cliff. 
Th*3 second range of hills may be said to extend from the 
parish of Llan-Asa, in an irregular ridge, occasionally intersect- 
ed by dells, to the vicinity of Mold, where it approaches the 
third, range, Mostyn Mountains, conspicuous by its ancient 
Pharos. The hills around Holywell, the Halkin and Bulkeley 
Mountains, are included in this range. The name of Mill is 
much more applicable to these than the appellation of Moun- 
tain. Their slopes, and sometimes their summits, are culthated 
and adorned with neat cottages and gentlemens’ seats. This 
range is separated by deep valleys from the lower range. Its 
general structure seems to consist of beds of limestone, contain- 
ing marine remains, which are in many places covered by thick 
irregular beds of a siliceous slate, in some places passing almost 
into hornstone ; in other situations into a rock intermediate be- 
twen flinty-slate and clay-slate ; and this last, in the hills above 
in these lower beds some years ago, suspended the works, and these seams have 
not since been attempted. v 
