1209.) 
of that which is mixed with the coal. of 
Shropshire, and some other counties. 
2. Lead ore, of the kind called galena, 
is sometimes found spread in extremely 
thin leaves or pilates upen the coal; but 
the quanuty 1s too small, either to do 
good or harm. 
Spars, calcareous, and gypseous, 
cliefly the latter in very thin plates, are 
to be seen sometimes on the cual. When 
the gypseous spar abounds, its vitriolie 
acid furms with the coal in ‘the firea 
sulphur, which blacksmiths observe is 
injurious to their iron. | They therefore 
avoid making use of coal, which has the 
Sparry appearance, 
Of the Qualily of the Soal, 
of working ite 
The coal of this “equity is of that kind, 
which does not cake’ as that from New- 
castle-upon-Tyne, and several other Eng- 
Tish coais do. Tt falls to pieces, and 
does not agglutinate jn the fire, but it is 
stronger 1n texture, and is liable to be 
broken into small pieces, in getting, and 
in carriage. It is not of that caking 
quality; it makes a pleasant fire, which 
requires less trouble in the management, 
and burns brisker than the caking coal, 
and on account of these properties, is 
preferable for chamber fires, and culinary 
operations; and itis a good coal for all 
kinds of metallic processes. : 
There is a considerable difference in 
the different qualities of the different 
beds or measures of the main-coal. .The 
first, or upper bed, called the rocf-floor, 
is generally left as a roof to support the 
earth or cluuch above it, from falling. 
The secend bed, calied the tep-slipper, 
and the third and fourth beds, which, 
together are called the white-coal, are 
reckoned the best for chamber Ges: 
Next to them in goodness, are reckoned 
the eleventh and twelfth beds, called 
sawyer and slipper ; alter them come the 
eighth, ninth, and tenth, called the foot- 
coal-stone coal, and Sohn coal. The 
tows and benches are preferred for ma- 
king the coaks, with which iren ore is 
smelted, and are therefore preserved for 
the furnaces. They do not kindle and 
flame so vividly as some of the foregoing 
measures; but they give a more durable 
and stronger heat, These two measures 
contain the largest proportion of fibres, 
resembling charcoal. The part of the 
Brassii Humphries, being the lowest 
measure, is that which is cut away, in 
order to let those above it fall down, 
and therefore most of it is reduced to 
paall coal, called sleek. 
_ The same beds of coal do, howe ever, 
2 
wv. 
and Method 
Mineralogy of the South-West of Steffordshire. 
yield less tar or oil. 
_ farities to which our coal is liab 
585 
differ in their quality in the different 
coal-fields, and even in eesti parts of 
the same field. In general, the collieries 
on the east side of the Dudley and Row: 
ley hills, yield better coal than those on 
the opposite side. ‘The coal is liable to 
diferent accidents. Sometimes it ap~ 
pears broken and crushed into small 
pieces, and is then calied mucks; some- 
times a bad quality, of a very. pee uliar 
nature, aifects a greater or less tract of 
coal, the limits of which are d: stinctly 
defived from the good coal on each side. 
‘Coal of this kind is called black, from’ its 
want of lustre, It gives less flame, and 
burns. less vividly than the good cual. 
I expect, that if it were distiiled, it would 
Among the singu- 
e, T must 
mention one, which, though of no cour 
mercial consequence, will nevertheless 
be reckoned curious by the miseralosist. 
It is a species of coal which ft have often 
observed in the cracks of the superin=. 
cumbent rocks and els which, though 
very bright and shining in Its appear- 
ance, gives little or no flame; in which 
‘respect it is similar to Kilkew iny coal, 
4 
and the Welsh culm, “But there is a cir- 
cumstance in its texture, which is pecu- 
har, or which-at least fis not been ob- 
served by mineralogists; which 1s, that 
the coal is embedded in small cubical 
cells, fermed by thin planes of calcareous 
spar, intersecting each other at right an. 
gles. M. Buffon, indeed, mentions a 
kind of coal dug at Alais, and in other 
parts of Languedoc, which contains so. 
much powder of calcareous earth mixed 
witheit, that it‘is burnt for the sake of 
the lime which is left; ~but there is no 
reason to suppose from his description, 
that the Languedoc coal possessed that 
singularity of. texture, which I have de- 
scribed. Buffon Histoire Natureile des 
Mineraurx ; ton. i. 
Tshali not by any means pretend tq 
give the art of mining, which admits of 
great mechanical detail, and much know- 
ledge derived from experience. I shall 
only observe, that the uncommon. thick- 
ness of this coal occasions a considerable 
difference in the method of working it, 
fram those employed at Newcastle, in 
Shropshire, and other countries, where, 
instead of ten yards, the veins of coal 
are only from five, six, seven, or eiwht 
feet thick. In order to support excava. 
tions ten yards hivh, it is necessangeto 
leave very large pillars of coal, éight or 
ten yards in diameter, which pillars vary 
however in size dnd tequeicy, -necorda 
lig 
