From Chapter Four
Coal is such a critical ingredient for the Industrial Revolution that a significant number of historians have ascribed Britain’s industrial preeminence almost entirely to its rich and relatively accessible deposits. Thomas Newcomen’s engine, after all, ran on coal, and was used to mine it. One would scarcely expect to read a history of the steam engine, or the Industrial Revolution, without, sooner or later, encountering coal.
Encountering it in the same chapter that documents the rise of the experimental method is, perhaps, a little less obvious. But that proximity is neither sloppiness nor coincidence: the two are subtly, but inextricably, linked. The relationship between science and technology, as Kelvin observed, is a two-way street. The mechanism by which the steam engine was first developed, and then improved, was a function not only of a belief in progressive improvement, but of an acute awareness that incremental improvements could be measured by reducing cost; demand for Newcomen’s steam engine was bounded by the price of fuel per unit of work.
For a million years , the fuel of choice for humans was hydrocarbons, in the form of both wood and charcoal, but it did no work, in the mechanical sense. Instead, it was used exclusively to cook food, and combat the cold. Several hundred thousand years later, a group of South Asians, or possibly Middle Easterners, discovered that their charcoal fires also worked pretty well to turn metals into something easier to make into useful shapes, either by casting or bending. For both space heating and metalworking, wood, the original “renewable” fuel, was perfectly adequate; measured in British Thermal Units – as above, the heat required to raise the temperature of one pound of water 10F – a pound of dry wood produces about 7,000 BTUs by weight; charcoal about 25% more. Only as wood became progressively scarcer did it occur to anyone that its highest value was as a construction material, rather than as a fuel. It takes some fourteen years to grow a crop of wood, and burning it for space heating or for smelting became a progressively worse bargain.
Europe’s first true “wood crisis” occurred in the late 12th century as a bit of collateral damage from a Christian crusade to destroy the continent’s tree-rich sanctuaries of pagan worship and open up enough farmland to make possible the European population explosion of the following centuries. A lot more Europeans meant a lot more wooden carts, wooden houses, and wooden ships. It also meant a lot more wood for the charcoal to fuel iron smelters, since smelting one pound of iron required the charcoal produced by burning nearly eight cubic feet of wood. By 1230, England had cut down so many trees for construction and for fuel that it was importing most of its timber from Scandinavia, and turned to what would then have been called an alternative energy source: Coal.
Coal consists, most importantly, of carbon, but it includes any number of other elements, including sulfur, hydrogen, and oxygen, that have been compressed between other rock, and otherwise changed by the action of bacteria and heat over millions of years. It originates as imperfectly decayed vegetable matter; imperfect because incomplete. When most of the plants that covered the earth three hundred million years ago, during the period not at all coincidentally known as the Carboniferous, died, the air that permitted them to grow to unimaginable sizes – trees nearly two hundred feet tall, for example – collected its payback in the form of corrosion. The oxygen-rich atmosphere converted most of the dead plant mater into carbon dioxide and water. Some, however, died in mud or water, where oxygen was unable to reach them. The result was the carbon-dense sponge known as peat. Combine peat with a few million years, a few thousand pounds of pressure, several hundred degrees of heat, and the ministrations of uncounted billions of bacteria and it develops through stages, or ranks, of “coalification”. The shorter the coalification process, the more the final product resembles its plant ancestors: softer and moister, with far more impurities, by weight.
Thus, each piece of coal is unique, the result of both different plant origins, and of differing histories of pressure, heat, and fermentation. What they have in common is that they all share the same relationship between time and energy: Over thousands of millennia, hydrogen and hydroxyl compounds are boiled and pushed out, leaving successively purer and purer carbon. The younger the coal, the greater the percentage of impurities, and the lower the ranking. In 14th century Britain, lower-ranked minerals like lignite and sub-bituminous coals were known as “sea coal”, a term with an uncertain etymology, but whose likeliest root is the fact that the handiest outcroppings were found along seams leading along the River Tyne to the North Sea.
Long before concerns about particulate pollution and global warming, coal had PR problems. Almost everyone in medieval England found the smell of the sea coal obnoxious, partly because of sulfuric impurities that put right-thinking Englishmen in mind of the devil, or at least rotten eggs; by the early 15th century, it was producing so much noxious smoke in London that King Edward I forbade burning it, with punishments ranging from fines to the smashing of coal-fired furnaces. The ban was largely ignored, as sea coal remained useful for space heating, though distasteful. Working iron, on the other hand, required a much hotter burning fuel, and in this respect the softer coals were inferior to the much older, and harder, bituminous and anthracites. Unfortunately, along with burning hotter and cleaner – a pound of anthracite, with a carbon content of between 86-98% by weight, produces 15,000 BTU, while a pound of lignite (which can be as little as one-quarter carbon) only about 4-8,000 BTUs – hard coal is found a lot deeper under the ground. Romans in Britain mined that sort of coal, which they called gagate, and we call jet, for jewelry, but interest in deep coal mining declined with their departure in the 5th century. It was not until the 1600s that English miners found their way all the way down to the level of the water table, and started needing a way to get at the coal below it.
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