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holgate: some physical properties of coal. 
It will be apparant that we must expect to find gradations 
from the pure caunel to the ordinary bituminous coal, and this 
is what we do find in fact. 
The coal known as the Better Bed, the first seam above the 
Elland flagstone, and also a portion about 8 inch thick in the middle 
of the Middleton Little Seam are nearly allied to the cannels. They 
are the coals known in the text books as being made up in a great 
measure of spores of coal measure plants. The coals are black and 
dull in appearance, and if scratched give not a black but a distinctly 
brown streak. If broken transversely the spores may be plainly seen 
in immense quantities protruding from the broken face, and a micro- 
scopic vertical section shows distinctly the resinous spores, for they 
are about the size of a pin's head. If we polish a piece of it as 
marble is polished, which we can do, the resinous spores which are 
tougher than the other part protrude slightly and show figures on 
the polished surface. Both seams contain fish remains, and the 
spores have every appearance of having floated into their present 
position along with a little mud. 
These coals are so tough, that when thrown down or struck, the 
pieces do not readily break, but ring sonorously. Their toughness 
and strength seem to be due in a great measure to a small quantity 
of the animal hydro-carbons together with resinous matter emanating 
from the spores that has permeated through the mass. 
In a fire which burns at a low temperature, such as a house fire, 
these coals are considered as almost valueless, for the individual bits of 
coal do not fuse together ; the fire does not burn brightly, nor does the 
ash fuse into clinker, but it flies about the house as a disagreeable white, 
fine dust. Its behaviour in a boiler furnace is better, but it will not 
make steam rapidly unless the draught be very great, the tempera- 
ture not being high enough to derive the best results from it. 
It is used to best advantage in a furnace working at a high tempera- 
ture, as are the reverbatory furnaces for melting or heating iron and 
steel. When thrown into a furnace of this kind (in which case it 
has finished its work at upwards of 3,000 degrees of temperature, 
such being the heat of the melted metal or the bloom) it bursts at 
once into a flame which is so long that it passes through the re- 
