[DOWLING] THE FORMATION OF COAL ; 25 
cellular tissue remnants of the more resistant parts of the vegetation, are 
found generally in the duller parts of the coal and though originally 
this was as low in ash as the softer parts it now probably contains, 
most of the ash originally in the whole mass, since the jellied portion 
has no doubt lost part of its original ash by gravitation through to the 
firmer material beneath. The chemical variations in coal due to original 
composition seem to be influenced greatly by the physical character of 
the original mass. The softer vegetation seems to contain a lower 
percentage of carbon and is easily macerated and consequently more 
quickly subjected to the alterations of the decaying stage. 
Process oF DECAY. 
The initial change in the vegetal mass follows immediately after 
the death of the plant. The vital energy of the cells which throughout 
the living period was expended on the absorbing of carbon compounds, 
is then relaxed and compounds of carbon and oxygen are quickly formed 
as well as others including volatile hydrocarbons. Should there be a 
general loss of carbon dioxide the effect, that is if the process is main- 
tained for a long period, will be a general raising of the hydrogen and 
carbon percentage of the remaining mass. The hydrogen, however, 
when it is in excess is liable to be set free and to take with it some carbon 
which means the loss of both hydrogen and carbon, generally in the form 
of marsh gas, until they are reduced again to a point of greater stability. 
The decaying stage, then, appears to induce the liberation of carbon 
dioxide to a point at which the mass remaining is high in hydrocarbons 
and then the hydrocarbons being unstable give off volatile gases until 
stability is arrived at. Variations then in the resulting coal may depend 
largely upon the period or stage at which the process of decay was 
’ stopped. : 
Bacteriological fermentation which seems to be present in all decay 
apparently aids the production of carbonic acid, at the same time form- 
ing more stable hydrocarbon compounds in the mass. This, if proven, 
means that fermentation directly raises the hydrogen and carbon per- 
centages, possibly by forming from the complex mass definite compounds 
between the hydrogen and carbon and allowing compounds of oxygen 
and carbon to escape. 
The assimilation of hydrocarbons is common to both plant and 
animal life. In animal life large percentages of nitrogen are stored in 
the body cells, while in plants a much smaller amount is required. In 
the forms of life which we have in ferments a very small nitrogen con- 
tent is required, so that one function of fermentation seems to be the 
liberation of nitrogen from the mass as well as of carbonic acid gas. 
Humic acid, which arrests the process is also formed; but if the bog or 
