312 J. G. Goodchild—Formation of Coal-seams. 
component laminz have each structural characters of their own, 
marking them off from those above and below, ou remaining con- 
stant over wide areas. 
Much stress has been laid upon the aaa association that is 
said to exist between seams of coal and beds of fireclay. But every 
practical mining engineer must be well aware of the fact that the 
two kinds of rock are by no means universally associated. Thick 
beds of fireclay occur in the Argill Coal-field near Kirkby Stephen, 
Westmorland,’ without a trace of coal near. One such bed is thirty 
feet in thickness. On the other hand, in certain rich coal-fields 
such a rock as fireclay (or as gannister) is conspicuous by its 
absence. 
Having glanced at an outline of the facts, we may pass on to 
consider one of the various modes of formation of coal—the others 
referred to are so obvious that no one can well have any doubt as to 
their validity in the present connection. As an illustration of what 
takes place, we may consider the sequence of events that must obtain 
in the case of any large river that is carrying seawards the spoils of 
a riparian forest region. Such a river transports vast quantities of 
inorganic materials; as well as more or less floating animal matter, 
which is partly terrestrial, partly fluviatile, partly estuarine ; there 
is, in addition, variable quantities of vegetable matter of all kinds— 
big tree trunks, boughs, stems, leaves, fronds, spores and spore- 
cases, and all the miscellaneous deciduous vegetable matter that 
may be derived from every part of the forest region above. The 
river does not transport its heterogeneous burden at a uniform rate 
of motion, nor does it drop it all at the same place. Far from that. 
The coarser mineral sediment drifts seawards along the bottom for 
a time, but finally comes to rest at no great distance from the land. 
Some of the tree trunks that have travelled so far as to become 
water-logged at this point sink here; and, obeying the laws of 
gravity, they sink with their heavier ends downward and are 
eventually buried root downward in the coarse sediment. Most of 
the animal matter, which decomposes quickly, also sinks near, and 
may be buried along with the trees. The finer inorganic matter 
drifts in suspension farther out to sea, where it subsides in crescentic 
zones on the seaward side of the coarser material, and entombs such 
of the vegetable matter as may have become water-logged at that 
part. Farther out to sea, or where the submarine currents have lost 
most of their transporting power, the finest sediment, after rolling 
about in clouds for a time, gradually subsides to the bottom, and 
there entombs also such of the vegetable matter whose constitution 
has enabled it to travel so far. Seaward of the zone where this 
happens quiet and still water prevails on the sea-bed. Here the 
littoral forms of marine life do not commonly reach ; and here also, 
it is commonly assumed that little or no organic matter transported 
from the land ever reaches. Most of the animal remains that may 
have floated down the river have probably all sunk, and been 
1 <<On the Former Extension of Coal Measures over Edenside,’’ Trans. Cumb. and 
Westid. Assoc. No. vii. p. 163. 
