8 REMARKS ON THE VEGETATION OF THE 
these large pieces; but sometimes the nature of the shale, of which its sub- 
stance is composed, causes it to fall in portions of different thickness. It is 
to these falling pieces that the miner’s expressive term, /ettle-bottoms, ap- 
plies. 
a, a, Shale, containing trunks. 
6, 6, 5, Trunks, in situ. 
c, c, Two views of a fallen portion, or kettle-bottom. 
These fossil plants are from two to eight feet in circumference. The oc- 
currence of numerous impressions of leaves and fragments of plants, ob- 
served in various parts of the shale, of which the substance of these fossils 
is formed, is to me, I must confess, very difficult of explanation. Some 
years ago, a friend of mine found a kettle-bottom at Old Kenton Colliery, 
eighteen inches in diameter, coated with fine coal, the substance of which 
was entirely of mineral charcoal, with a mixture of earthy matter and py- 
rites. A portion of this specimen is in the Collection of the Geological So- 
ciety. It is much to be regretted, that hitherto none of these interesting 
fossils have been followed into the strata. We do not know how far they 
extend, or to what height they are standing *. 
In the coal districts of Scotland, among the troubles which affect the 
roofs of coal, there is one of a very singular form, known by the name of 
pot-bottom or cauldron-bottom, and from the size of from one to five feet in 
diameter. One of these is represented in the annexed diagram. 
* I have been informed, since the above was written, that Mr Woop of Killingworth 
has succeeded in tracing some of these stems several feet into the solid rock. 
7 
