1864. | Hutt on the Coal Resources of Great Britain. 35 
the limit of depth within the last-mentioned figure. The means by 
which the temperature even at 4,000 may be reduced so as to admit 
of healthful labour is ventilation, and the question remains, to what 
extent can this be accomplished. A series of interesting experiments 
undertaken at my request by Mr. Bryham, at Rose Bridge Colliery, 
Wigan, enables us to arrive at the following general conclusion :—that 
in a mine of ordinary extent, the temperature can be lowered by 
20° or 30°, according to the distance from the shaft, and the season 
of the year. The cool air of winter reduces the heat of the mine more 
than that of summer time, so that even with a depth of 4,000 feet it 
may be often impossible to excavate the coal except during the colder 
months of the year. 
Space will not admit of our doing more than to glance at the past 
history and future prospects of coal-mining. It may be said that up 
to the end of the last century, the art had only smouldered. It was 
when the invention of the steam-engine revolutionized the industry of 
this country, that mining burst forth with an energy previously un- 
approached. Probably not more than ten millions of tons of coal 
were raised at the commencement of this century; yet in 1830 the 
quantity raised was thirty millions, and in 1851 not less than fifty-four 
millions.* From 1854 downwards, we have the returns of the Mining 
Record Office,t which show a general tendency to expansion, though 
with fluctuations ; the maximum having been reached in 1861, when 
the enormous quantity of eighty-six millions of tons was brought to 
the surface. 
Notwithstanding these facts, however, it would be rash to assume 
that the experience of the past is to be a criterion of the future. We 
neither wish for, nor expect, an increase during the remainder of this 
century at all proportionate to that of the earlier half, and this view is 
borne out by some of the later returns. Some of our coal-fields, as 
has been shown, have passed their meridian, and, having expended 
their strength, are verging on decay. Others have attained their 
maximum, or nearly so; this indeed is the case with the majority. The 
younger coal-fields will have much of their strength absorbed in com- 
pensating for the falling-off of the older; so that in a few years the 
whole of our coal-producing districts will reach a stage of activity 
beyond which they cannot advance, but around which they may 
oscillate. Entertaining these views, I am inclined to place the pos- 
sible maximum of production at one hundred millions of tons a year ; 
and yet it has been shown that even with this enormous “output,” 
there is enough coal to last for eight centuries. 
* On the authority of Mr. J. Dickinson, Her Majesty’s Inspector of Coal 
Mines. 
+ ‘Mineral Statistics,’ 1854-61. 
p 2 
