406 On the Porcelain Clay and Buhr-stone 
The buhr-stone itself, or entrochital horn-stone, is found near 
the middle of the eastern ridge of Halkin mountain, and on the 
west side of the ridge, into which it penetrates with a dip of 
about one yard in six. Its present appearance presents a bed of 
about four yards thick, between two layers of a compact siliceous 
slaty chert, covered with a shivery siliceous shale. It dips east- 
wardly, like all the other strata on the mountain, which con- 
sist of limestone rock aud chert. The buhr-stratum is princi- 
pally of the same quality as the small mill-stone sent herewith, 
and attested by Dr, Traill (Certificate, No. 1); but rotten masses 
sometimes occur, and blocks are occasionally found of too close 
a texture for the miller; and some few are quite solid. Still the 
corallite structure pervades the whole: the entrochites being 
perfect and entire in some instances, while in the chief parts of 
the bed the casts alone remain; thus leaving the rock vesicular, 
and in this respect differing from the nature of the pores in the 
French buhr, which appear to have been caused by corrosion, 
their edges being rusty and impure, whereas those in the Halkin 
buhrs are of pure flint, and exceedingly sharp and hard. 
The quarry from which all the buhrs hitherto used have been 
procured, now presents a fore-breast of forty yards, and is of the 
same quality and thickness as at first, but has a thicker cover- 
ing of shale as it dips into the hill. At the distance of a mile 
to “the north- west, a second quarry is now opening, and appears 
similar in every respect to the former; and from fragments of 
buhr here and there found, with pieces of shale and “of chert, 
half concealed in the mountain turf, traces of the same stratum 
may be observed from the one quarry to the other. About half 
a mile to the south-east of the main quarry, in the same chert- 
formation, the buhr-stone is also seen to crop out; and in the 
valley at the foot of the ridge, where a thick bed of limestone 
forms the upper stratum, with a sub-stratum of chert, the miners, 
in their search for lead-ore, have met with the buhr-stone at 
the depth of 160 yards from the surface. 
In order to prove the Halkin buhrs, the discoverers had some 
made into mill-stones, which they set ‘up in a neighbouring mill 
in the borough of Flint} ; some were had by a mill-wright, and 
afterwards sent to a mill at Dunham-o’-th’ -Hill, mixed with 
French buhrs; and one Jarge buhr was shaped into a mill-stone, 
and put up at a mill at Ysceifiog. 
They considered it would require much time to prove the real 
character of the buhrs, and that it would be useless to endea- 
vour to make sales till this proof could be satisfactorily made, 
and therefore they took but little trouble in circulating the ob- 
ject of their discovery for nearly two years, when finding that 
the 
