Bituminous oil shales occur in the Calciferous Sandstones under lying the Carboniferous Limestone series. These shales are worked at the present time mainly in Linlithgowshire, and oil, wax, and ammonia are obtained by distillation. Broxburn and West Calder are important centres of this industry.
Ironstone occurs with coal in many places, and for long was worked to supply the iron industries of the Central Lowlands. The most valuable seams, such as the Blackband ironstone, which could be cheaply smelted because of the large amount of carbonaceous matter which it contained, are practically exhausted, and many of the clayband ironstones have been abandoned on account of the expense of working them. The native production of iron ore is, therefore, no longer able to meet the demands of the iron industry.
The great coalfields of the Central Lowlands, the large supplies of good iron-ore which formerly existed, the proximity of coal and iron to one another, and the accessibility of the whole region by means of the Forth and Clyde estuaries, the one facing Europe and the other America, are conducive to the great industrial development of this part of Scotland. The first iron works to be established were at Falkirk, where ironstone, wood for fuel, and water-power from the Carron, were all obtainable, and for a time these works were the most important in Europe. Iron-smelting has since moved westwards, but the momentum given to Falkirk by that industry has made it at the present day the centre of a district noted for its production of all kinds of iron goods.
With the development of the use of coal for smelting iron, Lanarkshire naturally became the centre of this industry, and among the towns which owe their importance to it are Coatbridge, Motherwell, Wishaw, and Airdrie. On the Ayrshire coalfield, where ironstone could also at one time be obtained, Muirkirk and Dairy are the centres of the iron-manufacturing industry. These two counties, and especially the first, are among the most important in the United Kingdom for the manufacture of steel. Since the rapid decline in the production of native ore, the accessibility of the Central Lowlands has rendered easy the importation of foreign ore.
In early times, Glasgow owed its importance to its situation on the fertile soils of the Clyde valley, and to the fact that it was at the meeting place of routes from the north, the south, and the east. Later on, its position with regard to the New World brought it much trade, which eventually rendered necessary the deepening of the river. Thus it became a great trading port, while the abundance of coal and iron in the neighbourhood facilitated the growth of shipbuilding lower down the river. The Clyde is now the chief
shipbuilding area in the world ; it produces over 30 per cent, of the total tonnage of the United Kingdom, and its ships are to be seen on every sea. The principal yards are at Clydebank, Dalmuir, Dumbarton, and Greenock.
The textile industries of Scotland were originally scattered over the whole country. Linen was manufactured where flax could be grown, and where water was abundant. The introduction of machinery and the necessity of importing raw material from the Baltic countries have, however, drawn the industry to the east coast, where it is established at Dundee, Dunfermline, and elsewhere. Dundee suffered greatly during the Crimean war by the suspension of the supply of flax from Russia, and began to import jute from India, the manufacture of which has now become its leading industry, although it has suffered somewhat in recent years from the competition of the Calcutta mills. Various branches of the woollen industry are carried on in and around Alloa, Paisley, Glasgow, and other towns ; while the manufacture of thread, which is extensively followed in Paisley, is the chief branch of the cotton industry established in the Central Lowlands.
Among other industries are engineering and the manufacture of machinery, both of which are important pursuits at Glasgow, Greenock, Paisley, Dundee, Edinburgh, and elsewhere. There are chemical works on several of the coalfields ; some raw sugar is still refined at Greenock, where it is imported from the West Indies ; printing is an important industry at Edinburgh, and paper is made in the neighbourhood, where clear water is abundant ; oil cloth and linoleum are manufactured at Kirkcaldy ; Dundee obtains from the Carse of Gowrie much of the fruit required for the preserves for which it is noted.
To sum up, the Central Lowlands, on account of their moderate elevation and easy accessibility, their not unfavourable climate, and their fertile soils, the stores of coal which they still contain, and the supplies of iron which they once possessed, have become the great agricultural and industrial region of Scotland. As they contain the capital of the country, and its great commercial centres, they represent a " pole of convergence," drawing people from all directions, even as the Northern Highlands, and, to a less extent, the Southern Uplands, sending people in all directions, represent " poles of divergence."