The coal-fields of Great Britain and Ireland occupy, in round numbers, an area of 11,860 square miles, or about one-tenth of the whole area of the land surface of the country. Within this area, and down to a depth of 4,000 feet, lie the main deposits of our available wealth. Some idea of the amount of coal underlying this area will be gathered from the table[2] on the next page.
This supply, amounting to over 90,000 million tons, refers to the exposed coal-fields and to workable seams, _i.e._ those above one foot in thickness. But in addition to this, we have a large amount of coal at workable depths under formations of later geological age than the Carboniferous, such as the Permian formation of northern and central England. Adding the estimated quantity of coal from this source to that contained in the exposed coal-fields as given above, we arrive at the total available supply. This is estimated to be about 146,454 million tons. To this we may one day have to add the coal under the south-eastern part of England.
Amount of coal in millions of tons to depths not exceeding Coal Fields of-- 4,000 feet.
South Wales 32,456 Forest of Dean 265 Bristol 4,219 Warwickshire 459 S. Staffordshire, Shropshire, Forest of Wyre and Clee Hills 1,906 Leicestershire 837 North Wales 2,005 Anglesey 5 N. Staffordshire 3,825 Lancashire and Cheshire 5,546 Yorkshire, Derbyshire, and Northumberland 18,172 Black Burton 71 Northumberland and Durham 10,037 Cumberland 405 Scotland 9,844 Ireland 156
It is important to bear in mind, that out of the 170 million tons of coal now being raised annually we only use a small proportion, viz. from 5 to 6 per cent. for gas-making. The largest amount (33 per cent.) is used for iron-smelting,[3] and about 15 per cent. is exported; the remainder is consumed in factories, dwelling-houses, for locomotion, and in the smaller industries.
The enormous advancement which has taken place of late years in the industrial applications of electricity has given rise to the belief that coal-gas will in time become superseded as an illuminating agent, and that the supply of tar may in consequence fall off. So far, however, the introduction of electric-lighting has had no appreciable effect upon the consumption of gas, and even when the time of general electric-lighting arrives there will arise as a consequence an increased demand for gas as a fuel in gas engines. Moreover, the use of gas for heating and cooking purposes is likely to go on increasing. Nor must it be forgotten that the quantity of tar produced in gas-works is now greater than is actually required by the colour-manufacturer, and much of this by-product is burnt as fuel, so that if the manufacture of gas were to suffer to any considerable extent there would still be tar enough to meet our requirements at the present rate of consumption of the tar-products. Then again, the value of the tar, coke, and ammoniacal liquor is of such a proportion as compared with the cost of the raw material, coal, that there is a good margin for lowering the price of gas when the competition between the latter and electricity actually comes about. It will not then be only a struggle between the two illuminants, but it will be a question of electricity _versus_ gas, _plus_ tar and ammonia.