William Smith Uses Fossils to Determine the Order of the Strata in England and Helps Develop the Science of Stratigraphy

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William Smith Uses Fossils to Determine the Order of the Strata in England and Helps Develop the Science of Stratigraphy

Overview

Stratigraphy, the study of rock strata, emerged at the beginning of the nineteenth century for both scientific and economic reasons. Although William Smith was the first to use fossils to trace a long series of strata over a large area, his practical rather than scientific approach meant that his work was not influential outside of England. Georges Cuvier and Alexandre Brongniart, however, were well established in the scientific community, and their slightly later research became the basis for most future work on fossils and geological history. Nevertheless, William Smith is usually remembered as the father of English geology and as a pioneer of stratigraphy.

Background

In the late eighteenth century scientists began to ask a new kind of question about the structure of Earth's crust. Before, they had only been interested in the physical and chemical origins of rocks and the valuable minerals that they contained. Now, knowing the historical order in which strata (layers of rock) had been deposited became an important part of geology, too. The addition of this new emphasis was primarily due to a German mining teacher named Abraham Gottlob Werner (1749-1817).

The order of Earth's strata had been studied from time to time on a local basis in previous centuries, but Werner was the first to endorse a general system that divided all rocks into four basic "formations," according to how long ago they had been deposited. (Since new rocks were almost always formed on top of old ones, the age of any layer was determined by its position relative to others.) As he was a teacher, his 1787 "short classification" was very influential and was used all over Europe. However, because Werner's categories were so broad, geologists still had to find a way to sort out the sequence of layers within each formation and to match up strata occurring in different geographical locations. The age of a rock could not be known from its appearance and chemistry alone, because the same types (such as limestone, clay, and sandstone) occurred over and over again throughout the strata. Some geologists suspected that fossils, if examined more closely, might offer a way to get around this problem.

Before 1800 fossils had generally not been studied by people who were interested in determining the order of strata. Geologists felt that any fossil could come from a rock of any age, because Christian belief held that the same animals had existed unchanged for all time. Early in the nineteenth century, though, some biologists in Germany and France began to claim that many fossils came from species that no longer existed. If extinction was real, then the animals that had existed in the past must have differed from period to period. Fossils could thus be used to date rocks and to determine whether strata in widely separated locations were part of the same formation.

Ironically, the first person to apply this principle to give a detailed geological description of a vast area knew little if anything of the scientific theories involved. William Smith (1769-1839) was an English surveyor and engineer who acquired an extensive firsthand knowledge of the geology of England while engaged on numerous contracts from the 1790s onwards. By 1799 he realized that fossils were the key to determining the order of the "Secondary" (now called Mesozoic) rocks around Bath, in southwestern England. He was then able to show that the same strata could be found across the country, following a diagonal line to the northeast, thus demonstrating England's regular and predictable geological structure. Lacking any formal scientific training, however, Smith was not interested in the fossils themselves or in understanding the historical development of Earth. His interest in geology came from economic motives instead.

In Smith's time the Industrial Revolution was well underway in England. In this period of economic and technological growth and change, there was a large demand for mineral resources such as coal, metals, and building materials. Large landowners hired men like Smith to help them find valuable deposits on their property, and so it was important for him to be able to predict what sort of rocks would be found in a given location, even at a great depth underground. This task required knowledge of the order in which the strata occurred as well as the ability to tell where in this sequence a previously unexamined mass of rock belonged. Not surprisingly, these objectives were the same as Werner's, since practical concerns dominated in both cases. An important difference, though, was that on the European continent subjects such as mining geology were taught in state-run technical schools, while in Britain engineers and surveyors like Smith received only a practical, on-the-job education. Smith's social and intellectual background played a major role in determining the impact and influence of his work.

Impact

William Smith exhibited his maps and fossil collections to practical and gentlemanly audiences alike on numerous occasions in the first decade of the nineteenth century. He was particularly aided by the patronage of Sir Joseph Banks (1743-1820), president of the Royal Society of London. For various reasons, however, it was not until 1815 that Smith published his fully colored, large-sized map of the strata of England, with written commentary in following years. Although Smith's map was generally acknowledged to be a great accomplishment, it was based on work that he had done almost twenty years earlier, without reference to academic geology. In the meantime, two distinguished French scientists had also discovered the value of fossils to stratigraphy and had already communicated their work to a scientific audience. The impact of Smith's contribution cannot be understood without reference to their work.

Georges Cuvier (1769-1832) was an important and influential biologist who was already famous for his work on fossils and extinction; Alexandre Brongniart (1770-1847) was a geology professor and the director of the state porcelain factory, which gave him an interest in finding deposits of material useful for making ceramics. Working together in the region around Paris from roughly 1804 to 1808, they combined their skills to establish a detailed stratigraphic sequence of Tertiary rocks, based on the different fossils found in each layer. They reported their results promptly in scientific journals, including an English translation in 1810 and a geological map in 1811.

Cuvier and Brongniart planned, executed, and communicated their research in a framework that made it easy for other scientists to understand and apply their conclusions. In addition, they used stratigraphy not just to locate mineral resources but to understand the geological and biological history of an area. For the first time it was possible to see what organic life had been like in the distant past and how it had changed in response to changes in the physical environment.

By the time William Smith finally published his map, four years after Cuvier and Brongniart's, the next generation of English geologists was already beginning to take an interest in the work of the French school. These scientists, exemplified by the Geological Society of London (GSL), which had been founded in 1807, were concerned with historical rather than practical questions. Thus, Smith's accomplishment, although it was a first, was not directly influential on geological thinking in either Britain or continental Europe. However, it should not be thus inferred that his impact was entirely negligible.

Smith did make an effort to communicate his work, if not through scientific journals. He spread his ideas through personal contact with other geologists, including his nephew John Phillips (1800-1874), who eventually became a professor at Oxford. Smith's methods were widely appreciated by practical men like himself, who used them in their regular work. Smith's methods also sometimes provided crucial information about local stratigraphy to the gentlemen scientists who were responsible for the major debates and developments in early nineteenth-century British geology.

Furthermore, in seeking to determine the order of the more complex strata that underlay the rocks studied by Smith, high-profile members of the GSL such as Adam Sedgwick (1785-1873) and R. I. Murchison (1792-1871) were continuing a project that he had begun, even if their terms and ideas were completely different. Although the gentlemanly GSL could not accept someone who labored for a living as a member, Sedgwick and Murchison acknowledged their own appreciation of Smith's work, and his impact on them, by awarding him in 1831 the GSL's first Wollaston medal and by calling him the "father of English geology."

Smith's 1815 map also had some impact. It covered a much longer sequence of strata and a much larger geographical area than Cuvier and Brongniart's. It also used an innovative colorshading scheme to convey the three-dimensional structure of the strata, a method that was technically superior but impractically expensive. Less usefully, Smith named the strata according to his own personal terminology rather than attempting to connect them with already described formations elsewhere in Europe. This was one way in which his work had very limited impact, since geologists wanted to establish historical interpretations and mapping standards that would be applicable everywhere. Finally, if nothing else, Smith's map demonstrated the basic value of fossils as a powerful tool for solving stratigraphical problems. For example, it is likely that Brongniart himself saw a preliminary version of the map while visiting Joseph Banks on a trip to London in 1802 and was encouraged by the possibility of such a project.

The development of stratigraphy was arguably the most important event in the history of early nineteenth-century geology. With this tool, geologists were able to construct a complete, synthetic history of Earth, realizing for the first time just how long a period of time the fossil record represented. This theme was taken up by Charles Lyell (1797-1875), and it later found a place in the theory of natural selection, implying that the ultimate intellectual and social impact of the use of fossils in stratigraphy have been truly immense. More immediately, though, there were real economic benefits of knowing where to look, and where not to look, for coal and other resources. The desire to find and exploit mineral wealth motivated the establishment of numerous state geological surveys around the world from the 1830s onwards, and the ability to make accurate and useful maps was an important part of this movement.

The use of fossils in stratigraphy was thus valuable to different people for different reasons. William Smith's contribution is best measured by his own practical standards, according to which it was a notable success. Cuvier and Brongniart's work was equally successful by their newly developed historical standards, which were also quickly becoming those of the geological community at large.

BRIAN C. SHIPLEY