Sunday, March 1, 2009

T6. More on early coal mining

In the last Tech Note I wrote about harvesting coal along the coast, and then the shallow workings that became the first underground mining, where tunnels were driven into the sides of the hills, within the coal seam. The miners would load the coal into baskets, or corves. These corves were woven by people in the village, it was one of the early jobs that George Stephenson (he of railway fame) had at the mine. And they were small enough that they could be carried by women. (The quote at the bottom of the post says that they carried 56 lb of coal). As greater production was needed, so the corves grew larger, and were placed on sleds that women and children could drag through the mine to either the outside, or, as the seam went deeper, to shafts. At the shaft the coal baskets would be raised to the surface using windlasses, which were turned either by people, or as more power was needed by horses or oxen. You can see a corve being lowered using a horse gin in this picture .

As the workings moved away from the shaft, a layout had to be created in which pillars of coal would be left to hold the roof up. At the same time there were two gases that became feared by the miners. At the time they were using candles that were attached to spikes that could be driven into the coal wall, or a wooden prop being used to hold the roof up. One of the gases that would desorb from the coal is methane. This is the natural gas that is now, in some locations collected by drilling long horizontal holes through the coal. It is an unconventional source of gas, and usually called Coal Bed Methane (CBM). While it will come out of a pipeline at a useable concentration, when it seems out of the coal within the mine it can become diffused through the air, and in a modern mine the air speed and volume are designed to dilute it, and carry it rapidly out of the mine. In earlier years, however, they did not have such fans. The air was almost still, and so the methane could rise and collect in pockets at the roof. Holding up a candle to see ahead a miner could ignite the gas, or if it was in a concentration of 5-15% by volume it could explode. When it explodes it can kill either through the force of the blast, or by burning up all the oxygen in the mine, suffocating those not initially killed.

At the start of a miner’s day they might therefore send someone in, wrapped in wet cloth, and crawling along the floor with a candle on a stick. At each high point in the roof he would raise the candle, hoping in this way to burn out the gas, before it reached the explosive level, and while the pockets of gas were small. The person doing this was given the title “The Penitent. ” The role was also present in salt mines faced with the same problem, and there is a photo of a Polish model, the old classic picture is a bit harder to find so I must dig out and add a version of my copy.

Keeping the air churned so that these pockets of what was called Fire Damp, or just plain damp, had to be done several times a shift, generally by waving an article of clothing, in the days before mine ventilation.

The other gas that had to be watched for was carbon dioxide, which in contrast with methane, which being lighter than air collects in the roof, is heavier and thus pools on the floor. So that if you were getting down to cut the starting slot in the bottom of the coal seam, you might just drop into a pool. It was called choke damp – though that was also the name given to carbon monoxide, which could also seep out of the coal. All these gases are colorless and odorless so that without some form of detection (the canary for example, or using a candle as a test) they can lurk to catch the unsuspecting. With the invention of the safety lamp (where the heat of the flame is removed by a surrounding mesh of copper wire) it became possible to use the lamp itself as a testing tool. One of my first mining tests was to make sure that I could tell, by the height and shape of the small blue flame of the methane burning over the lowered flame in the lamp, what the gas concentration was. (Each lamp was in a separate hood, and I remember that they had two at the same concentration in the set of around half-a-dozen I had to evaluate).

As the mines grew larger air had to be circulated through them, so that these gases would not build up, and a series of temporary and permanent walls would be built between pillars in worked out areas of the mine, to make sure that the air moved around the mine, and then back out the shaft. For many years, starting in around 1810 the motive power for the air was created by having a fire in the bottom of the shaft, in a special furnace room. Usually these were underground, although there was the occasional one at the surface. Unfortunately if the fire ignited the surrounding timber that was being used for support, then a major fire could result, killing everyone underground. This was the case with the Avondale mine disaster in 1869, at the time the worst industrial accident in American history, 110 people died.

Although there are still parts of the world where this type of primitive mining still occurs, and where women and children are used to help get the coal out, in most countries they have been banned from underground work. (This was the Act of 1842 in the United Kingdom) . Taking the coal from the miner or hewer to the shaft was known as putting or hurrying. (I learned it as putting).
Six year old girl:
"I have been down six weeks and make 10 to 14 rakes a day; I carry a full 56 lbs. of coal in a wooden bucket. I work with sister Jesse and mother. It is dark the time we go."

Jane Peacock Watson.
"I have wrought in the bowels of the earth 33 years. I have been married 23 years and had nine children, six are alive and three died of typhus a few years since. Have had two dead born. Horse-work ruins the women; it crushes their haunches, bends their ankles and makes them old women at 40. "

Maria Gooder
"I hurry for a man with my sister Anne who is going 18. He is good to us. I don't like being in the pit. I am tired and afraid. I go at 4:30 after having porridge for breakfast. I start hurrying at 5. We have dinner at noon. We have dry bread and nothing else. There is water in the pit but we don't sup it.

So I will leave this segment just as the mine transitions from families working where the man hews coal from the face, loads the baskets, which are then dragged to the shaft by his wife and children and winched to the surface. Next time I will talk about the coming of the pit pony and mechanization and the changes that made. It increased the energy cost of mining the coal almost from the beginning, but that’s next time.

Earlier posts on coal mining are:

T1. Coal – its formation and structure

T3. Coal Reserves – or what can I count as real?

T5. Historic Coal Mining.

As I get time (and practice) I will also come back and illustrate these words with some pictures using Poser.

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