Sunday, February 22, 2009

T5. Historic coal mining

In trying to lay a foundation for later posts I am using these Sunday Tech Talks to cover points that folk may not be aware of. As the debate over coal continues, and likely intensifies over the next couple of years then I will revisit topics such as: where it is; how it can be mined; how we should burn it; and what we do with the products. Along the way I will also talk a bit more about the energy and other societal costs of coal, but for today I am going to go back to where mining started.

When coal was first used, the legends have it that it was collected along the sea coast near Tynemouth, and taken to the local priory and the rights to the coal were given to the monks. Coal was used to provide the fire for the local lighthouse until about 150 years ago. The monks did well by their ownership of the coal rights, by 1281 they were shipping the coal down to London where it brought nineteen shillings a chauldron. (There were 20 shillings to a pound, which is currently worth $1.44, though the value has historically been higher). A chauldron was a wagon that would hold around 80,000 cubic inches of coal or just over 45 cu. Ft. of coal, or about 1.7 tons of coal. So we know that coal was heading down to London, where King Edward (because the fumes apparently sickened his mother) banned it, with the threat of torture and death to those that used it. (This is the king that had Wllliam Wallace, as played by Mel Gibson in Braveheart, chopped into bits, while alive, so he generally wasn't someone you wanted to mess with). But is was sufficiently cheaper than the wood alternative that the ban had little effect, and coal has been a major fuel in the United Kingdom ever since.

The king, incidentally, was compensated in other ways, since a royal duty was imposed on the mining and shipping of coal, that brought in a large income over the years. In 1818 the mines were estimated to produce 15 million tons a year, for domestic use, with additional amounts used by industry. The duty was 9 shillings and four pence to London, and 6 shillings to other ports in the UK. And this brought in a revenue of 570,066 pounds in 1816. Some 2.25 million chauldrons of coal were shipped, roughly half of which originated in Newcastle.

Mining had progressed by that time from the initial collection of loose coal washed up on the beach (sea coal) to mining it where it outcropped, and then mining back into the seam outcrop from the surface, and this often meant that the tunnel that was mined sloped down into the ground. The dirt that was mined out was dumped at the entrance to the tunnel, and often created a small narrow feature on the ground, a tip, some of which can still be seen today. Our family, for example, used to be coal miners at Eglingham. This is a small village found in the North East of England, not that far from the Scottish border.
Aerial view of North of England (Google Earth)

I have marked an overview of the village with a couple of arrows to show where the two tips were that I have walked around (and where my ancestors no doubt worked) on an overall view of the village (using Google Earth) which is at the bottom of the picture.
Eglingham (Google Earth)
Right in the center of the picture however, of one zooms in until GE tilts a bit, you can see a third tip quite clearly.
Pit tip at Eglingham (Google Earth)
My aunt (the Teacher) had done some research on where we lived, and this was not down in the current village but up where the top left arrow points, and where all that is left of the houses are circles where the gorse grows, but where rabbit warrens have brought up small pieces of china, and other remnants of the time that folk lived there, only a couple of hundred years ago.
Ruins at Tarry, near Eglingham
In those days it was pre-mechanization, and the miners used only a pick and a shovel to break the coal from the solid. It was then put into woven baskets called corves, that were dragged to the surface on a wooden board, either by younger boys, or by women. The board would slide up the tip, and could be dumped before being dragged back underground. The tunnels were driven to the height of the coal, which in the area may have been somewhere around 4 ft 10 inches (with an interbedded layer of stone that ranged from 3 inches to 2 ft thick) or 5 ft 8 inches, (with 3 ft of interbedded stone) not the richest of workings.

In these small operations, with all the excavation from the initial tunnel into the side of the hill, the coal was mined by individual workers, or families. The miner would work with a candle as a light, and that would be mounted to a wooden post that he would use to hold the roof up.
Miner position (when I relearn Poser I will put in a better illustration)

Laying on his side, he would then take his pick and cut out a slot at the bottom of the coal. This undercut would be cut along the total face of the coal, before the miner would start to work up. Depending on the size of the tunnel he may also make a vertical cut to create a second free face. (You can see some of these markings in the walls of old stone quarries, and in the mines under Bath in the UK, and the salt mine at Wieliczka in Poland). He would then break out the coal in individual lumps that were several inches in size. (4-6 would be ideal). If he used the joints (called cleat) and the bedding planes of the coal, then this was not too difficult to do, and so he could mine out several chauldron’s worth of coal in a shift. In the measurement of the work he did using a modern measure it would take as little as 4 joules/cc of energy to break out that coal.

A typical shift would be around 8 hours, but it shrank, so that when I went into the mines it lasted only 7.25 hours. As well as mining the coal, the miner had to hold up the roof, and, if there was a roof fall repair it. But of all his concerns the most prevalent was that of gas. Remember both that he had to breathe, and that coal emits methane, or natural gas, from most seams. The methane will burn, or in the right concentrations in the mine can explode. And when that happens it consumes all the oxygen, so that even if the miners aren’t in an area where the explosion happened then they may still die as the de-oxgenated air circulates underground.

Sadly, just today I heard that there had been such an explosion in a mine in China. While I don’t know much about this particular incident, it is something that can be quite difficult to fully protect against, since there are many ways that the gas can get into the working area, and so much of the safety precautions are aimed more at making sure that it is not ignited if it does become present. Our sympathies and prayers are with them and their families tonight.

I will return to talk more about coal mining and the next step up in the size of operations, in a later post, For the North of England, after these smaller surface workings were exhausted, larger mines such as the Scremerston Colliery grew nearby to produce coal on a larger scale, My ancestors moved on to Ashington, and the coal mines there, of that also more anon.

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