The Supply and Waste of Goal. 319 



are affected by faults and the dip of the strata. A brief notice 

 concerning each of these conditions will prepare the reader for 

 a consideration of the inquiries suggested by the title of this 

 article, namely the probable extent of the supply of coal in our 

 own country, and the degree of economy exercised in getting 

 and using the mineral fuel. 



1. The quality of the coal. This depends to some extent 

 on the uses to which it is to be applied, for although all fair 

 coal is usable for most purposes, and saleable, the value differs 

 enormously. Thus an excellent household coal may be but a 

 poor gas coal, and the converse; a good steam coal adapted for 

 locomotives may be indifferent for furnace-work ; and so with 

 regard to ail. Coals consist of carbon, with a certain admixture 

 of hydrogen, and some oxygen and nitrogen. There is also a 

 certain quantity of siliceous and earthy matter forming the ash. 

 Coals that consist of pure or nearly pure carbon, require so 

 strong a draft to keep up combustion, and give out heat so 

 intensely at a short distance, that they require very peculiar 

 contrivances for using them economically, and thus anthracite, 

 as such coal is called, has but a local reputation. Cannel-coal, 

 again, yielding an enormous quantity of gas, is by no means 

 economical fuel for the open fire of an ordinary grate, or for a 

 steam furnace. The heat is not sufficiently concentrated. 

 Coals yielding a large quantity of ash are, in like manner, 

 undesirable, for much of the caloric produced by combustion is 

 wasted in keeping the earthy ash at a red heat. Thus the 

 value of a coal must be estimated locally, and is strictly relative, 

 though in general no coal could be considered bad in which the 

 quantity of ash is not more than six or seven per cent., and 

 where the per-centage of volatile substances does not exceed 

 twenty-five per cent., and amounts to ten per cent. With less 

 volatile matter than ten per cent, it is anthracite, and with 

 more than twenty-five it passes into cannel coal. In either 

 case the uses are special. Most of the English and Scotch 

 ooals are of sufficiently good quality to be available for general 

 purposes, but the money value varies. The Welsh coals are to 

 a large extent anthracites. 



2. Number and thickness of the seams. Coal exists in beds 

 of all degrees of thickness, from, a tenth of an inch to at least 

 fifty yards. It is evident that there must be a practical limit 

 to economic working, and that under certain circumstances it 

 may be expedient and profitable to work seams that under 

 other circumstances could not possibly pay. When worked by 

 shafts in the ordinary way, it is sometimes worth while to 

 remove coal not more than a foot thick • but this is rarely the 

 case, for so much stone and rubbish has to be moved to mine a 

 seam of this thickness, that the work is not profitable. In 



