We have seen elsewhere what it is in the dust which makes it dangerous, how that, for the most part, it consists of the dust-like spores of the lepidodendron tree, fine and impalpable as the spores on the backs of some of our living ferns, and the fact that this consists of a large proportion of resin makes it the easily inflammable substance it is.  Nothing but an incessant watering of the workings in such cases will render the dust innocuous.  The dust is extremely fine, and is easily carried into every nook and crevice, and when, as at Bridgend in 1892, it explodes, it is driven up and out of the shaft, enveloping everything temporarily in dust and darkness.

In some of the pits in South Wales a system of fine sprays of water is in use, by which the water is ejected from pin-holes pricked in a series of pipes which are carried through the workings.  A fine mist is thus caused where necessary, which is carried forward by the force of the ventilating current.

A thorough system of inspection in coal-mines throughout the world is undoubtedly urgently called for, in order to ensure the proper carrying out of the various regulations framed for their safety.  It is extremely unfortunate that so many of the accidents which happen are preventable, if only men of knowledge and of scientific attainments filled the responsible positions of the overlookers.

CHAPTER V.

EARLY HISTORY—­ITS USE AND ITS ABUSE.

The extensive use of coal throughout the civilised world for purposes of heating and illumination, and for the carrying on of manufactures and industries, may be regarded as a well-marked characteristic of the age in which we live.

Coal must have been in centuries past a familiar object to many generations.  People must have long been living in close proximity to its outcrops at the sides of the mountains and at the surface of the land, yet without being acquainted with its practical value, and it seems strange that so little use was made of it until about three centuries ago, and that its use did not spread earlier and more quickly throughout civilised countries.

A mineral fuel is mentioned by Theophrastus about 300 B.C., from which it is inferred that thus early it was dug from some of the more shallow depths.  The Britons before the time of the Roman invasion are credited with some slight knowledge of its industrial value.  Prehistoric excavations have been found in Monmouthshire, and at Stanley, in Derbyshire, and the flint axes there actually found imbedded in the layer of coal are reasonably held to indicate its excavation by neolithic or palaeolithic (stone-age) workmen.

The fact that coal cinders have been found on old Roman walls in conjunction with Roman tools and implements, goes to prove that its use, at least for heating purposes, was known in England prior to the Saxon invasion, whilst some polygonal chambers in the six-foot seam near the river Douglas, in Lancashire, are supposed also to be Roman.