Coal is the remains of ancient plant life fossilized into a combustible substance, being made up mainly of Carbon, Hydrogen, Nitrogen, and Oxygen, with Carbon being the major element.  Coal was laid down in 'Seams' or 'Veins' hundreds of millions of years ago, in geological periods known as the Devonian & Carboniferous. During this time the lands were covered with extensive forests and vegetation. This vegetation was entirely different to today's vegetation, in that there were no trees as we know them, but giant 'Tree ferns' or Calamites, which were nevertheless, close to a hundred feet high. These were, over a period of millions of years, drowned by the sinking of the land, covering their remains with silts, these silts became the layers of rock or clay type of substance between the seams of coal. The land then rose again, growing a new layer of vegetation, which eventually also became drowned and fossilized to become the seams of coal we have today, and which extend from near the surface in some places to hundreds of yards below the ground in others. In Britain, the thickness of seams ranges between one and a half feet to thirty feet, while in other parts of the world they can be several hundred feet thick. A cubic yard of uncut house coal would weigh around one ton. which would equal 1016 kilos.  Early man was to dig with flint tools, bone implements, and antlers. They gave the history of mining by leaving their tools behind so that we have each stage of the industry to look back on. They cut tunnels into the hills called 'Levels' or 'Drifts' going into the hillsides to obtain coal. The problem of water was usually solved by making use of the natural slope of the workings, which allowed the water to flow away by gravity. This sometimes meant driving another drift into the lower parts of the workings from a lower point. Old underground workings are still found today, with tunnels and timbers being hundreds of years old still in place.