this amount of coal were erected in a pyramid,
its square base would extend over 40 acres, and the height would be 3356
feet.

There are grounds for believing that the produce of the various
coal-fields of the world does not at present much exceed 100,000,000 of
tons annually, and therefore our own country contributes more than
three-fifths of the total amount. If we divide the coal-yielding
counties of Britain into four classes, so as to make nearly equal
amounts of produce, we find that Durham and Northumberland yield rather
more every year than seven other counties, including Yorkshire.
Derbyshire, again, produces more than eight other counties, and nearly
as much as the whole of North and South Wales, Scotland, and
Ireland--the yield of the latter being about 17,000,000 of tons, and
that of the two first-named about 16,000,000 of tons.

In 1773 there were only 13 collieries on the Tyne, and these had
increased to upwards of 30 in 1800. The number of collieries in 1828 had
increased to 41 on the Tyne, and 18 on the Wear, in all 59, producing
5,887,552 tons of coal. The out-put of coal in Northumberland and Durham
in 1854 was no less than 15,420,615 tons, and now in these two counties
there are 283 collieries. Mining began on the Tyne and continued on the
Wear, where the industry has been largely developed. There are in all
about 57 different seams in the Great Northern coal-field, varying in
thickness from 1 inch to 5 feet 5 inches and 6 feet, and these seams
comprise an aggregate of nearly 76 feet of coal. Taking the area of this
field to be 750 square miles--a most probable estimate--we may classify
the contents as household coal, steam coal, or those employed in
steam-engine boilers, and coking coal, employed for making coke and gas.
Of household coal there is only 96 square miles out of the total 750,
all the remainder being steam or coking and gas coal. The greater part
even of this 96 square miles has been worked out on the Tyne, and the
supply is rapidly decreasing also on the Wear, where the largest bulk
of the household coal lies. The collieries of the Tees possess but six
square miles out of the 96, as far as we at present know. Turning,
however, to that part of the coal-field regarded as precarious, and
consisting of first, second, and third-rate household coal, we have for
future use 300 square miles. London was formerly supplied from the pits
east of Tyne Bridge, where is the famous Wallsend Colliery,