[DOWLING] THE FORMATION OF COAL 31 
only twenty per cent of the original mass, so that the ash would be mag- 
nified over four times. This would indicate that coals should have high 
ash and does not seem reasonable when we find coals containing as low 
as two or four per cent of ash when the vegetable material from which 
it was derived had only from one to two per cent. 
We therefore assume that pressure has prevented a waste of carbon 
and for confirmation of this we turn to the experiments being made in 
the reduction of modern peat to a higher grade fuel. In the charring 
of peat to make charcoal there is a great loss; but in the processes in 
which the wet peat is subjected to pressure and heat either in furnaces 
or by superheated steam, it is definitely stated that no volatile com- 
bustible gasses are formed during the operation of raising the carbon 
percentage. 
If this is true combinations between oxygen and hydrogen and 
oxygen and carbon must have been formed. The formation of water, 
in this way, increases the carbon of the solid matter but leaves it slightly. 
low in hydrogen. Should there be a small per cent of carbonic acid gas 
formed, the hydrogen would be raised to the normal and the alteration 
would then follow that outlined in the diagram, and coals of various 
grades will be formed depending on the relation between the amounts 
of these two that are eliminated. If carbon dioxide is freely formed, 
fatty coals result or if only small amounts are dissolved and carried 
away in the water formed, lean coals or those with low hydrogen 
are formed. For the general average the proportion by weight 
would be #:0_ 7 
CO} woh 
This entails a loss up to a possible 6 per cent of the carbon and will 
not unduly raise the ash percentage. 

We have in this way outlined two extreme cases in which coals 
could be formed—the one wasteful and the other much less so. It is not 
to be supposed that the majority of the coals could be classed as having 
been formed altogether in either of these methods; but examples possibly 
could be found which would approximate in character the expected 
resultant of either. The majority will possibly show a range of ash 
(not taking into consideration any possible material from extraneous 
sources, such aspartings in seams which denote a subsidence or flooding) 
which will indicate some loss of hydrocarbons; but not of any great 
amount, the alteration being due largely to the elimination of oxygen 
compounds. 
The formation of coal from the peat stage depends mainly on the 
application of pressure maintained for long periods—the alteration being 
hastened by heat. Extreme alteration or loss of oxygen is found in the 
anthracites which, especially in America show relatively higher ash than 
the bituminous coals of the same formation. This suggests that their 
