184 WHAT WE OWE TO OUR COAL-FIELDS. 



rising in economic importance. Those yielding alum and 

 copperas (the alum and pyritous shales of the miner) have 

 long been worked, though on a small scale, but now the 

 bituminous shales, or those yielding paraffin and paraffin oil, 

 are eagerly sought after and worked on a gigantic and rapidly 

 extending scale. Fields in the lower Coal-measures of Scot- 

 land, which half-a-dozen years ago did not bring a farthing 

 to their proprietors, are now yielding thousands ; and the 

 distillation of these shales may already be regarded as an 

 established branch of our national industry. ISTor is it 

 merely as sources of a new and brilliant light that these 

 shales acquire their importance. Recent experiments have 

 proved the adaptability of their crude oils as a fuel for 

 steam-raising, and the hope is now held out that even the 

 inferior varieties may be turned to good account in lessen- 

 ing the pressure upon our more precious coal-seams. In- 

 deed, when we consider the worthless aspect of these 

 shales and the beauty and utility of the substances solid 

 paraffin, paraffin oil, naphtha, rosine and magenta dyes 

 derived from them, few instances of human ingenuity to 

 utilise the products of nature could be adduced, at once so 

 marvellous and so thoroughly successful. What so unlike 

 as a block of black bituminous mudstone and a paraffin 

 candle, white and translucent as the finest wax 1 ? What 

 so seemingly impossible as the extraction of a brilliant 

 rose-purple dye from a mass of pitch-coloured coal-tar 1 



Besides these rocks the coals, ironstones, limestones, 

 sandstones, fire-clays, and shales of which the Carbon- 

 iferous system is entirely composed, there occur in some 

 localities independent veins of lead -ores and zinc -ores 

 traversing the beds of the mountain limestone. These 

 veins (like those r of Derbyshire, Yorkshire, and Northum- 

 berland) are often of great commercial value, not only for 

 the lead and zinc they directly supply, but for the per- 



