NOTES ON COAL AND FUEL. 163 
it open, and in such quantity as to be sufficient for the use of the 
neighbourhood. «. 
The beds of coal are of various thicknesses, from a few inches to 
several feet ; and in some places, it is found advantageous to work them 
at a very great depth, although their thickness does not exceed four or 
five feet. The thickest bed of English coal, of any extent, is that of the 
main coal in the mines of Bilston and Dudley, Staffordshire, which 
measures from thirty to forty feet. In many places there are several 
beds above, and parallel to, each other, separated by strata of slate, 
sandstone, and other minerals. Coal is never found in chalk, and very 
rarely in limestone. 
At Whitehaven, the principal entrance to the coal mine, both for 
men and horses, is by an opening at the bottom of a hill, through a long 
passage hewn in a rock. This, by a steep descent, leads to the lowest 
bed of coal. The greatest part of the descent is through spacious 
galleries, which intersect other galleries, all the coal having been cut 
away, except large pillars, which, in deep parts of the mine, are three 
yards high, and about twelve yards square at the base, such great 
strength being there required to support the ponderous roof. There are 
three distinct and parallel strata of coal, which lie at a considerable 
distance above each other, and which have a communication by pits 
that are sunk between them. These strata are not always regularly 
continued in the same plane. The miners occasionally meet with veins 
of hard rock which interrupt their further progress, and at such places 
the earth on one side of the vein appears to have sunk down, while 
that in the opposite side has its ancient situation. These breaks 
miners call "dykes." When they come to one of them, their first 
care is to discover whether the coal, in the part adjoining, be higher or 
lower than that in which they have been working ; or, to use their own 
terms, whether it be cast down or cast up. For this purpose they 
examine the mineral strata on the opposite side, to see how far they 
correspond with those which they have already passed through. If 
the coal be cast down, they sink a pit to it ; but if it be cast up, the 
discovery of it is often attended with great labour and expense. 
In general, the entrance to coal mines is by perpendicular shafts, 
and the coal and workmen are drawn up by machine^. As the mines fre- 
quently extend to great distances horizontally, beneath the surface of 
the earth, peculiar care is needed to keep them continually ventilated with 
currents of fresh air, for the purpose, not only of affording to the work- 
men a constant supply of that vital fluid, but also to expel from the mines 
certain noxious exhalations which are sometimes produced in them. 
Some writers have imagined coal to be the remains of antediluvian 
timber, which floated upon the waters of the deluge, until several strata 
of mineral substances had been formed ; others conceive it to have been 
antediluvian peat bog. It is now, however, universally admitted, that 
coal is nothing more than vegetable matter, which flourished when 
