140 
Coal-field from Leeds by Bradford, Halifax, Huddersfield, 
and Deepcar, and in the fire-clays which underly some of 
the coal seams. Some of the Millstone Grit and other stones 
also resist moderately high temperatures. The Ganister is 
a hard, siliceous sandstone ; the best qualities contain about 
97 per cent, of silica. 
In the vicinity of Leeds, it is worked at Meanwood, and 
at Laister Dyke, near Bradford. Though the Meanwood is 
not equal to Sheffield ganister, it is so near, that the cost 
of carrying the Sheffield ganister to Leeds outweighs its 
superiority. It is full of the rootlets of the trees which have 
formed the coal seams, generally found overlying it ; it breaks 
into irregular pieces, without stratification, being very hard 
and brittle, and it cannot be used for building purposes. It 
is ground for the purpose of lining cupolas for melting iron, 
furnaces for melting steel, and Bessemer converters. In all 
these it has to be often replaced, as it cracks away ; but it is 
not suited for making crucibles for steel or glass, because it 
would crack away too rapidly, or fall into a powder. It is 
ground and mixed with fire-clay and other sandstones, to 
make what are called silica bricks ; though these are used 
for very high temperatures, they can only be used where the 
temperature is constant and regular, and are not suitable for 
furnaces which are subject to great and rapid variations in 
temperature, as they crumble to pieces. 
The bricks made from the fire-clay which is found among 
the Ganister measures underlying the Halifax Hard -bed coals 
at Shipley, near Bradford, is, perhaps, the best suited for 
building reverberatory furnaces ; while those made from the 
clay found in the same measures in the neighbourhood of 
Huddersfield, have long held the reputation of being the best 
for glass furnaces, and I think would also build good iron 
furnaces, as they expand and contract without cracking, and 
do not form into drops so much as many other fire-bricks do. 
