OCCURRENCE OF COAL WITH UNUSUAL CONDITIONS 319 
full of large and small plant fragments, were deposited simultane- 
ously between these patches. The vegetable mud which later 
formed the coal was originally of about the same thickness as the 
intervening sands and was intertongued into them. Subsequently 
the vegetable mud was compressed to only a small fraction of its 
original thickness, but the sands were affected to a limited extent 
only. 
AMOUNT OF REDUCTION IN THICKNESS OF ORGANIC DEPOSITS IN 
CHANGING TO COAL 
Observations on several occurrences in the cut as to the relative 
amount of compression of the coal, as shown by the equivalent 
thickness of sandstone, give widely conflicting results. 
ke of Coat | TLaeat ol eat | Hau of Cale 
cera sien OT Le 3-4 inches 46 inches 1 to 114 to 15 
Fy la elit cca Ret eRe ree 13? inches 30 inches 1 to 17 
Big Why Ge eae eee g-a inches 15 inches I to 60 to 120 
ANSE totes ian eres 4 inches 20 feet t to 60 
Giacs Sa lorena nse 5 inches 31 inches a 10) (0) 
* Thin coal streaks are prominent in the sandstone in the last case. 
There are, however, certain factors which explain this variation 
in large part or entirely, although they do not allow a precise deter- 
mination of the actual reduction in volume in the process of coal 
formation. In certain of these occurrences, there are many thin 
stringers of coaly material involved in the sandstone where its 
thickness was measured, and these also suffered reduction of vol- 
ume, so that the thickness of sandstone given does not necessarily 
represent the original thickness of the adjacent column of plant 
mud. It cannot be said that these are more important in the first 
two instances and help to explain the relatively smaller thickness 
of sandstone there found; but they do explain in part the small 
thickness of sandstone in No. 5. Asa matter of fact, the first two 
seem to indicate most nearly the actual reduction in thickness of 
the coal. There is a yet more uncertain factor involved in the 
inclined bedding of the sandstones, to be discussed below. 
