74 
Barnsley bed, it has been possible to push explorations nearer 
to the probable extinction of the seam than in that of the 
Silkstone coal. 
At this point, the rapid deterioration of the seam has 
forbidden any attempts to work it ; and a tract of unexplored 
ground is entered upon, beyond which, as has been already 
mentioned, the Barnsley coal is represented on one side by 
the Warren House, and on the other b}' the Gawthorpe, 
which differ strikingly both from the Barnsley bed itself and 
from one another. 
On the horizon of the Barnsley coal then there are 
changes still more striking than those met with in the case 
of the Silkstone seam. When the equivalent coals in different 
parts of the field are compared with one another, the 
representative beds are found to be tliree in number, and no 
two of these are in the least degree alike. 
It now remains to offer some explanation of the probable 
manner in which changes like these just described are 
produced. 
The occurrence of partings in a bed of coal, and the 
variations in thickness of these partings, are easily accounted 
for. Coal, it is well known, is the result of an accumulation 
of dead vegetable matter which grew on swampy flats at the 
spot where it is now found. When accumulation had gone 
on for some time, the ground was lowered and submerged 
beneath water. Into this water, sand and mud were carried 
by running streams, were piled up into banks, or spread out 
n layers, and covered up the sheet of dead vegetable 
material. Then upheaval followed, a land surface was again 
formed, and on it the growth of a fresh seam of coal took 
place. If the submergence was of long duration, the two 
successive coal beds are separated by a considerable thickness 
of shale and sandstone ; but where the depression lasted for 
only a short time two beds of coal are formed, separated by a 
