districts. "Dyke" is the word most commonly used in the north of England, and "trouble," "slip," and other similar terms, often occur. In South Staffordshire the word "thing" is very commonly used instead of "fault." They speak of an "upcast" or "downcast thing."
I am not exactly aware how far "fault" and its synonyms may be used accurately in other mining districts, but in South Staffordshire both "fault" and "thing" are terms which are used by colliers, ground bailiffs, agents, and all concerned with them, in the most vague and puzzling way. These terms are applied to matters of the most incongruous natures, so incongruous that it is impossible to include them under any one general term without introducing great confusion of ideas, and consequently falling into all sorts of blunders in practice.
For instance, we have already seen that a cake of sandstone included in a mass of coal is called a "fault," and though in the preceding pages it has always been spoken of as a "rock-fault," yet that limitation or specification of its nature is not one commonly used in the district. Again, the "rolls" or "swells" in the floor of the coal are called "faults." Mere partial and irregular thickenings or thinnings of a bed are spoken of as "faults." I have even heard the natural outcrop of a bed of coal at the surface, especially if it rose to the crop a little more suddenly than usual, spoken of as "the fault" by many old miners of the district.
One of the most eminent and long experienced coal and iron masters of South Staffordshire gave, as his definition of a fault, on a legal examination, "anything which interrupted and deteriorated the coal." Under this definition dykes and intrusive masses of "green rock" (or trap) would be called faults.
A very intelligent ground bailiff once described to me a "sand fault," which I could not understand till I found it meant the outcropping of the New mine coal into a mass of drift at a depth of 90 feet below the surface.
Mr. Keir, in his account of the district, evidently applies the term "fault" not to the mere fracture and displacement, but to the substance, whatever it be, that comes in between the walls of the fissure, or the substance that is met with in place of the coal. This idea of a substance of a different kind from that expected seems to be the prevailing one attached to the word fault, for not only do they call "faults" things such as those above, but I have on several occasions had true faults, such as the Brockmoor or Corbyn's Hall fault, described to me as "not really a fault, but only a slip."
Examples of the great pecuniary loss and practical blunders likely to arise from this confusion of ideas might be easily accumulated. I will select two. In the case of the gap in the Thick coal at the Gower colliery, described in page 45, it is clear that whatever cause it was which destroyed the coal, that cause had ceased to act before the Cat heath, or the bed immediately above the Thick coal, was formed; yet the ground bailiff who described it to me was surprised that the fault did not affect the Brooch coal
