162 NOTES ON COAL AND FUEL. 
the name of the pit, near Newcastle, whence they are obtained, usually 
bear the highest price. 
Common Coal or Pit Coal, is of a black colour, and has generally a 
slaty structure and foliated texture. When handled it stains the fingers ; 
and when burnt it cakes more or less during combustion. Its com- 
ponent parts are usually charcoal and bitumen, with a small portion of 
clay, and sometimes with pyrites, or sulphuret of iron. What is called 
slaty coal contains a greater portion of clay than other kinds. 
Some foreign writers have ascribed the great wealth possessed by 
England to the coals which are there found in such abundance, and 
which facilitate, in a very essential degree, nearly all its manufactures, 
and consequently are a means of promoting its commerce to an extent 
which is possessed by few other countries. All Britain's great manu- 
facturing towns, Birmingham, Sheffield, Leeds, Glasgow, &c, are situated 
either in the midst of coal districts, or in places to which coals are 
conveyed, with little expense, by canal carriage. 
The extraction of saleable coal from British mines approaches a 
hundred millions of tons per annum, and the waste of coal involved in 
getting this quantity is probably more than one-fourth part more. Coal 
weighs rather less than a ton to the cubic yard, and we are therefore 
removing and using, or destroying, from the portion of our own small 
island to which coals are limited, 125,000,000 of cubic yards every year 
of one of the most valuable substances in existence. Assuming a coal 
seam to have an average thickness of two yards, it would take twenty 
square miles of such a seam to supply one year's consumption. It 
behoves us, then, to look around and consider the resources we possess, 
whether we can afford to expend this portion of the capital stock of our 
national wealth, and what chance there may be of this local supply 
becoming exhausted. 
Coals in England are principally obtained from the neighbourhood of 
Newcastle-upon-Tyne, Sunderland, Derby, and Stafford. Glamorgan 
likewise furnishes a considerable supply of coal : it having been esti- 
mated that the coal fields of South Wales extend over 1,200 square miles ; 
and those of Northumberland and Durham 732 square miles. The 
particular places whence they are obtained have the name of "collieries, " 
and the mines from which they are dug are called "pits." The deepest 
of these are in Northumberland, and are worked at more than 900 feet 
below the surface of the earth. At Newcastle there is a coal-pit nearly 
800 feet in depth, and which, at that depth, is wrought five miles 
horizontally, quite across and beneath the bed of the river Tyne, and 
under the adjacent part of the county of Durham. At Whitehaven, the 
mines are of a great depth, and are extended even under the sea, to 
places where there is above them sufficient depth of water for ships of 
great burthen, and in which the miners are able sometimes to hear the 
roaring of the water. On the contrary, in some parts of Durham the 
eoal lies so near the surface of the earth that the wheels of carriages lay 
