A Short History of Coal
Coal yields more energy per ton than wood, but it is difficult and dangerous to extract from the ground. Consequently, wood was the main fuel for industrial and domestic use until the eighteenth century.
Few deep mines were dug before 1700 – flooding was a significant problem, and the presence of combustible gases made illumination extremely difficult.
Estimates of coal production vary, but around 3 million tons of coal were extracted in Britain in 1700, and this had only risen to four and a half million tons by 1750. By 1800 about 10 million tons were dug, with about 16 million tons produced by 1815 and 30 million tons by 1830
But coal was one of the vital ingredients of the industrial revolution, and the innovative spirit of the eighteenth century was applied to coal just as much as to every other aspect of industry.
Lighting the Way
The pumping engines developed by Thomas Savery and Thomas Newcomen began to resolve the problem of flooding in the mines, but the problem of lighting remained until well into the nineteenth century.
Eye strain was a real problem for miners. Often candles were used for illumination, but mines produce toxic and flammable gases, and explosions were common.
To try and deal with the methane and other flammable gases that seeped into mines, firemen were employed. Dressed in dampened leather or wool suits, these men carried a lighted taper on a long pole through the mine. The colour of the flame would change in the presence of gas, and the mine could be ventilated to allow the gases to escape. At other times the taper was used to ignite the gases. It can't have been a very safe job.
Another way of providing some illumination, introduced in the 1730s, was to spin a metal disk against a flint. The sparks emitted provided some illumination and, supposedly, had a lower risk of igniting the flammable gases. However, some explosions were caused by this method.
Sir Humphrey Davy, the famous chemist, and inventor, developed a safety lamp in 1815 which used wire gauze to contain a flame. Unfortunately, the gauze quickly rusted in the damp conditions of a mine, and the lamp became unsafe.
George Stephenson, before he became a famous railway engineer, also developed a safety lamp in 1815. It used different principles to Humphrey Davy's but was also prone to damage. Better safety lamps followed.
The problem of lighting mines remained until the early 1900s with the introduction of electric lighting and torches.
Coal, Coke, and Iron
Traditionally iron was smelted using charcoal. But charcoal was expensive and large quantities were needed for the iron industry.
Coke is made by heating coal in the absence of air –similar to the way charcoal is made from wood. Coke was used to roast malt for the beer industry from the late 1600s and, in the late 1690s, a young Abraham Darby was apprenticed to a man who supplied mills to grind malted barley.
By 1702 Darby was working in the brass industry near Bristol. He developed a way of mass-producing brass pots and, from 1705, he began to apply his expertise to casting iron. He took out a patent for his new casting method in 1707.
His brother in law had a brassworks at Coalbrookdale in Shropshire, and Abraham Darby moved to the area in 1708 and leased a furnace. He began to experiment with producing iron using coke rather than charcoal. He was lucky in that the coke produced from the local Shropshire coal was of high quality.
Darby was successful, and his business expanded. Sadly, Abraham Darby died in 1717, but the business continued to be run by members of his family. His son Abraham Darby the second took the business over when he was old enough – in 1728 – at the age of seventeen.
Abraham Darby, the second, expanded the business further and was succeeded by his son Abraham Darby the third in 1768. He provided the iron castings for the famous Iron Bridge built in 1781 near the Coalbrookdale works. The Iron Bridge was a kind of giant advertisement for the company's work and for cast iron. He also improved pay and conditions for his workers, building housing for them and even buying local farms to supply the workforce with food.
Although Abraham Darby, the third, died in 1789, the family continued to manage the business until it was finally subsumed into a larger iron working operation in the mid-1800s.
Abraham Darby and his descendants pioneered the production of iron using coke from 1709, but the practice didn't become widely used in the industry for another forty years.
We met John Wilkinson earlier. He invented a method for boring iron in 1774 and became the exclusive manufacturer of the piston cylinders for Boulton and Watt's steam engines.
Wilkinson was one of the most successful ironmasters of the eighteenth century. As well as the iron boring machine, he invented a rolling mill, and a hydraulic powered blowing engine for blast furnaces. He owned several iron foundries and also invested in copper and lead mines, and he was a strong promoter for the building of the famous Iron Bridge across the River Severn. Opened in 1781, this was the first cast-iron bridge in the world. In 1787 he launched the first iron boat in the world.
By the mid-1790s, Wilkinson's iron foundries are believed to have been producing around one-eighth of the cast iron in Britain.
Perhaps unusually for the age, Wilkinson was a good employer. He built cottages for his workers and their families and sought to ensure that miners who supplied him received a fair return.
John Wilkinson, nicknamed Iron Mad Wilkinson, died in 1808 and, unsurprisingly, was buried in a cast-iron coffin.
Cast Iron vs. Wrought Iron
Cast iron is molten iron poured into a mould. It is strong in compression and, therefore, useful in bridge arches and supports. Many bridges were built in cast iron in the early industrial revolution starting with Abraham Darby the third and John Wilkinson's famous Iron Bridge at Coalbrookdale.
However, cast iron is brittle in tension and prone to fracture. As we have seen, early attempts at building steam railways were hampered by the rails cracking under the weight of the engine.
Wrought iron is worked iron, it is a more refined iron hammered or rolled to improve its quality. Wrought iron is strong under tension but was much more expensive than cast iron as, before the middle of the eighteenth century, it had to be worked by hand.
John Wilkinson, Henry Cort, and others developed mechanised mass-production methods of producing wrought iron, which greatly reduced the cost.
In 1821 John Birkinshaw patented a method of producing wrought iron rails in a rolling mill. George Stephenson understood their importance and used them in the Stockton and Darlington Railway, and his later railways.
Wrought iron rails, along with improvements in engine technology, enable the railway age to flourish.
James Beaumont Neilson
We close this lesson on coal, coke, and iron with James Beaumont Neilson.
Born in Glasgow in 1792, he worked in the coal and iron industries. He experimented with the smelting of iron and realised that blasting air heated to 600 centigrade into the furnace was much more efficient than the methods previously used – cutting consumption of coal by a third.
Patented in 1828, Neilson's hot-blast method allowed coal to be used in iron smelting rather than coke. It also allowed black-band ironstone to be used as a source of iron ore. Since coal was much cheaper than coke and the previously unusable black-band ironstone was prevalent in the central belt of Scotland and elsewhere across Britain, Neilson's advances opened up the massive growth of the iron industry in the UK.
Although not widely known today, Neilson's advance was certainly one of the most important developments in the industrial revolution.
Thank you for listening to this lesson. In our next lesson, we move onto developments in civil engineering.