260 
ASHLEY : NOTES ON ADWALTON AND HALIFAX COAL. 
by roots and rootlets which are in all probability those of the 
plants whose dead tissues formed the coal. The ganister is, in 
fact, a sandy soil which has been exhausted by the removal of its 
iron and potash salts by the plants which grew upon it. 
These two seams furnish examples of coal of widely different 
origin, and while the " driftwood " theory is probably correct in 
the case of the cannel it cannot be accepted in that of the 
Hard Bed. 
Some of the sections are taken from the memoir of the 
Geological Survey on the Yorkshire Coal Field, others being 
obtained from information kindly given by Mr. Walter Rowley, 
F.G.S. The writer wishes to express his sincere thanks for the 
valuable suggestions and help received from Mr. A. R. Dwerryhouse, 
B.Sc, F.G.S. 
