as a domestic fuel.  It has been used as a fuel in various processes of manufacture, and the lignite of the well-known Bovey Tracey beds has been utilised in this way at the neighbouring potteries.  As compared with true coal, it is distinguished by the abundance of smoke which it produces and the choking sulphurous fumes which also accompany its combustion, but it is largely used in Germany as a useful source of paraffin and illuminating oils.  In Silesia, Saxony, and in the district about Bonn, large quantities of lignite are mined, and used as fuel.  Large stores of lignite are known to exist in the Weald of the south-east of England, and although the mining operations which were carried on at one time at Heathfield, Bexhill, and other places, were failures so far as the actual discovery of true coal was concerned, yet there can be no doubt as to the future value of the lignite in these parts, when England’s supplies of coal approach exhaustion, and attention is turned to other directions for the future source of her gas and paraffin oils.

Beside the Bovey Tracey lignitic beds to which we have above referred, other tertiary clays are found to contain this early promise of coal.  The eocene beds of Brighton are an important instance of a tertiary lignite, the seam of surturbrand, as it is locally called, being a somewhat extensive deposit.

We have now closely approached to true coal, and the next step which we shall take will be to consider the varieties in which the black mineral itself is found.  The principal of these varieties are as follows, against each being placed the average proportion of pure carbon which it contains:—­

  Splint or Hard Coal, 83 per cent.;
  Cannel, Candle or Parrott Coal, 84 per cent.;
  Cherry or Soft Coal, 85 per cent.;
  Common Bituminous, or Caking Coal, 88 per cent.;
  Anthracite, Blind Coal, Culm, Glance, or Stone Coal, from South
    Wales, 93 per cent.

As far as the gas-making properties of the first three are concerned, the relative proportions of carbon and volatile products are much the same.  Everybody knows a piece of cannel coal when it is seen, how it appears almost to have been once in a molten condition, and how it breaks with a conchoidal fracture, as opposed to the cleavage of bituminous coal into thin layers; and, most apparent and most noticeable of all, how it does not soil the hands after the manner of ordinary coal.  It is at times so dense and compact that it has been fashioned into ornaments, and is capable of receiving a polish like jet.  From the large percentage of volatile products which it contains, it is greatly used in gasworks.