1872.] The Coal Commussioner’s Report. 45 
whilst at depths below 4000 feet it is computed that there is 
a further supply amounting to 7320 millions of tons, which 
might be obtained if existing obstacles to working at a lower 
depth than 4000 feet were overcome. Space will not admit 
of our even touching on the considerations upon which the 
Commissioners express themselves in favour of finding coal 
under the permian and newer strata. The supply from 
this source, within the depth of 4000 feet, is roughly esti- 
mated at 56,273 millions of tons. It is also considered 
probable that coal measures may possibly extend beneath 
the south-eastern part of England; but Sir Roderick Mur- 
chison contends, in opposition to this theory, that ‘‘ in con- 
sequence of the extension of Silurian and Cambrian rocks 
beneath the secondary strata of the South-east of England, 
and of the great amount of denudation which the carbonife- 
rous rocks had undergone over the area of the South of 
England previous to the deposition of the secondary forma- 
tions, little coal could be expected to remain under the 
cretaceous rocks.” As this question is still one of theory, 
no attempt has been made by the Commission to estimate 
the quantity of coal lying under the unexplored area of the 
South of England. 
Omitting the probable amount of coal below 4000 feet in 
depth, there thus appears to be an aggregate quantity of 
146,480 millions of tons which may be reasonably expected 
to be available for use ; and it remains now only to see how 
long that quantity, with an increasing consumption, is likely 
to last. The bases upon which calculation may be made, 
as to the probable duration of our coal supplies, are nume- 
rous, and varying conclusions have been consequently 
arrived at by different authorities. The two great principles 
upon which such a calculation should be based are—the 
annual increase in population, coupled with the increase in 
consumption of coal per head of the population. Now, 
from the year 1811 to 1821 the increase in population was 
16 per cent, while in the last decade, from 1861 to 1871, it 
was 11% per cent. These two rates of increase, in con- 
junction with those of the intervening decades, have been 
taken as the elements of a curve which, carried forward, 
shows the extent of the population in future years, supposing 
no disturbing causes to arise. The rate of consumption of 
coal per head of the population appears to have been very 
irregular; but, on an average, the increase in fourteen years 
‘amounts to nearly 3 per cent per annum, but it is not thought 
probable that this rate will be maintained. From statistical 
tables furnished by the Commissioners, it appears that the 
