Learning from old science books: Part One

Hello readers! Last week I read a Victorian geology book – possibly one of the most influential science books ever written. Principles of Geology by Charles Lyell introduced a relatively young field to a general audience, and solidified geology as a science in its own right, rather than as a mere rock collecting exercise. It was published in three whopping volumes between 1830 and 1833, and soon became the standard introductory textbook to the subject, with ten subsequent editions over the following decades. As you can probably imagine, much of the “science” that it contains has now been thoroughly debunked – so you might be wondering why anyone would bother trying to read it, or why it belongs on a science fiction blog.

For me, there are a number of lessons to be learnt from old science books. Principles of Geology captures the state of geological sciences in the 1830s, and provides insight into old methods and theories, as well as revealing the priorities of Victorian scientists through their unanswered questions, and their recommendations for future research. It also discusses older theories, which are now so outdated and thoroughly debunked that we have all but forgotten them. Reading this book forces you to imagine the world from the perspective of someone who didn’t know about evolution, about climate change, or about plate tectonics. It puts your concept of fact into perspective, and challenges the confidence with which we infer processes from observations. Faced with the same rocks, the same data, but with a different foundational understanding of the world, people can come to starkly different conclusions. The most logical solution in 1830 is no longer the most logical solution in 2025 – and this makes you wonder what the most logical solution will look like in 2225.

As a science fiction author, I see old science books as a valuable resource. If you want to make predictions about the technologies and concepts of the future, it is worth diving into the scientific past, to appreciate how quickly things can change.

So, even if you have no particular interest in Earth science, I hope you can gain something from this quick dive into Principles of Geology. Take a moment to step into the shoes of an 1830s scientist, and imagine how your own beliefs might be viewed by scientists 200 years from now.

Because this is such a long book, covering so many topics, this post is part one of two (or three – no promises). This week, I’ll provide some context for the influence of this book, and the state of geological knowledge at the time of its publication. I’ll then discuss one of its key themes: the variation in climate through geological time. Next week we’ll deal with fossils, igneous rocks and volcanoes (in order of excitement).

Is this… Popular science?

Principles of Geology was hugely influential. In fact, many of Charles Lyell’s key ideas are still taught in schools today. However, the ideas were only part of the reason for its success. Within minutes of picking up this book (an abridged version – I doubt I could lift all three original volumes in one go), I realised that it wasn’t really a textbook. Instead, it reads like a popular science book, intended for a broad, naïve audience. The descriptions are colourful, the writing is engaging (certainly by Victorian standards, and even by modern scientific standards), and it is filled with examples and references to processes which ordinary people would recognise and understand. Yes, it has three volumes and a questionable lack of structure – but wealthy Victorians had much more patience than modern readers, and plenty of time on their hands.

The book sold well at the time, and it was read widely – not just by the scientifically inclined. Apparently, it had a profound effect on poets, who were blown away by the proposed vastness of geological time (which probably felt even vaster with a healthy side of laudanum). The book convinced more people to study Earth and environmental sciences; in fact, Charles Darwin was so greatly inspired by Lyell’s work that he went on to overturn vast swathes of it in his revolutionary, and decidedly more famous, On the Origin of Species (1859). Lyell’s book turned geology into a respected science, rather than an obsessive rock collection disorder. Although, let’s face it: obsessive rock collecting is still the cornerstone of geological research.

Geology in the 1830s

Charles Lyell published Principles of Geology at a time when geology was seen as a heretical field, attempting to disprove the facts of the Bible. It was also deemed by many scientists to be too fantastical and qualitative, with little basis in facts or reason. After all, nobody was around to witness the ancient past. Anyone could make up a story about it – because how could they be proven wrong?

In 1830, there was already a foundational textbook for geologists: Theory of the Earth, by James Hutton (of unconformity fame). It had been around since 1788, but had a tarnished reputation. Hutton had proposed an endless rock cycle, and devout Christians were infuriated by the concept of a world without beginning or end. Hutton’s work was viewed as most heretical – an attempt to disprove the existence of god. Christian geologists set out to prove him wrong, and started presenting various geological formations as evidence for the great flood.

The geological sciences descended into a battle between “vulcanists” and “neptunists” – people who believed that igneous rocks came from volcanoes, and people who believed that igneous rocks had crystallised from water (don’t laugh – we can only assume that their houses were plagued by extreme limescale). Later, geologists started reporting “diluvium” across Europe, which were sedimentary deposits believed to have formed in the great flood.

This was the state of science when Charles Lyell wrote Principles. He became a leading figure in opposing the fruitless search for flood evidence, and in debunking the notion that igneous rocks had precipitated from water. The industrialisation of Europe, and particularly the UK, led to a boom in geological surveying, providing scientists such as Lyell with more observations on which to base their ideas, and discredit the neptunists.

Still, one of the reasons that Principles became so popular was because it never attempted to disprove the existence of god. Charles Lyell was staunchly Christian – and he made it very clear that he had nothing to do with heretical vulcanists. Yes, there was no geological evidence for the flood, and yes, the world was older than had once been believed, but he was adamant that the universe was the work of some divine architect. His book reframed geology as a physical science, akin to physics or chemistry, with no religious agenda, and this made it palatable to a general Christian audience.

Geological science, according to Lyell:

“The present is the key to the past.”

Anyone who has studied geology has probably heard this phrase, or seen it in size 24 Comic Sans MS on a poorly structured PowerPoint slide. This is the key concept introduced by Charles Lyell – the tenet that turned geology into an evidence-based, analytical science. He deemed the constancy of natural laws to be the most important truth, and asserted that the forces observable today must also have acted in the past. So, a geologist can infer the environment in which a sandstone formed based on their observations of modern environments, in which sandstones are currently forming. The full title of the book says it all: “Principles of Geology, being an attempt to explain the former changes of the Earth’s surface by reference to causes now in operation.”

Lyell’s method for geological interpretation is taught in schools to this day. I can still remember the GCSE class in which I first heard this simple phrase, because I found it so eye-opening. When you look at rocks, you are looking at the products of processes – and if you’ve seen enough of the world, you can imagine these processes in operation, having seen them first hand (e.g., ripples forming in the mud on an estuary), or having seen something similar (e.g., clay baking in a kiln). Lyell insisted that if we interpret rocks based on irrefutable observations of present-day processes, there is no need, or temptation, to make anything up.

The present is the key to problems…

There are obvious pitfalls in Lyell’s alluringly simple method. The laws of physics have probably been constant since the dawn of time, but natural processes, such as tides or winds, are the products of a tremendously complicated Earth system. By asserting that only the processes currently observable can be sure to have existed in the past, Lyell ruled out the possibility that conditions may have once been different (e.g., stronger tides), or that they may be different in future (e.g., higher concentration of carbon dioxide in the atmosphere). This stance was somewhat paradoxical, as we will soon discover. It was never quite clear what he deemed to be constant, and what he viewed as an acceptable fluctuation.

This self-contradiction is present throughout Lyell’s book, and is no more evident than in his views on climate, which we will discuss in the following section. Nevertheless, his simple yet powerful mantra has remained highly influential ever since it was published, and has become an unshakeable constant in its own right.

Climate, according to Lyell

By the 19th century, geologists across Europe were starting to realise that many of the rocks beneath our feet could only have formed in warm, tropical environments. Limestones contained tropical corals, coals contained tropical ferns, and although many rocks contained fossils of species that no longer existed, these fossils shared attributes with modern-day tropical creatures. All the evidence suggested that Europe had once been much warmer than it was today – and this posed quite a conundrum for scientists. Why had the climate changed? At first glance, this observation is directly at odds with Lyell’s insistence on uniformity – so it is no wonder that he required multiple chapters to explain his views.

In 1830, many scientists believed that the Earth was gradually cooling down after a fiery, molten formation. However, Lyell was very dismissive of this notion. He saw no way to prove that the planet had ever been molten, so he determined such a hypothesis to be mere speculation. He also pointed to evidence of cooler climates in recent history, including the remains of woolly mammoths, as proof that the climate varied, rather than following a systematic trend.

Lyell proposed that climate is controlled by the positions of continents, with regional variations dependent on proximity to the coast and to mountains. He supported his theory with evidence from the present day, and devoted a good portion of one chapter to a list of temperatures recorded across the world (all in Fahrenheit, rendering them utterly meaningless to me). He predicted that when high land collects in the polar regions, the global climate will be cooler – although he never explained why this should happen. There is a similar lack of justification in his assertion that the ratio of land to sea is always constant. He viewed large continents as “a necessary part of the economy of nature”, but didn’t explain why this should be the case. Uniformity was taken for granted.

The tectonic elephant in the room

For a modern reader, these climate chapters are overshadowed by a crucial, missing process. Lyell, and all geologists at the time, assumed that all land is fixed in position. Faults and earthquakes were known to shift rocks around by a few miles or more, but generally speaking, land was taken to be immobile. A limestone pavement currently exposed at 55°N was assumed to have always been at 55°N. So, given that the limestone formed in a tropical sea, it had to be assumed that the climate at 55°N was once tropical.

By assuming the position of the land to be constant, Lyell was forced to propose various mechanisms for extreme global variations in climate. However, a modern reader can see just how easily this assumption can be flipped around. If you assume that the global climate has been roughly constant throughout geological time, then it must have been the land that moved.

This was the crucial missing piece. But at the time, nobody had considered that the continents, so evidently huge and immovable, could travel (or should I say “drift”). The concept of continental landmasses rifting and shifting wasn’t fully accepted until over a century later – but today, the theory of plate tectonics forms the foundations of our geological understanding. We know that continents move over millions of years, traversing various climatic zones and collecting rocks along the way. We know that those tropical limestones did, actually, form in the tropics – and this is a much simpler solution than imagining a major climate shift allowing tropical reefs to survive in the high latitudes.

However, that’s not to say that Lyell was wrong to suggest dramatic, global climate variations. In fact, there is a good amount of evidence to suggest that the whole world was once locked in ice – maybe more than once (although this is still being debated). It is now widely accepted that the organisation of continents does impact the global climate and atmospheric composition, and the types of creatures that can survive. But although Lyell planted the seeds of these ideas, it took several decades for other scientists to get these seeds to bloom into concepts such as the albedo effect, the effect of ocean circulation, or the amplification of minor changes through positive feedback.

Strangely enough, Lyell’s hunch about the ratio of land and sea remaining constant was quite close to the mark, given his total lack of justification. Even the most basic diagrams of plate tectonics show that continents are never destroyed, and that oceanic crust is the only material that gets created, subducted and remelted. By modern reckoning, the continents are fairly constant, which is why they are so much older and more complex than the crust beneath the oceans. By lucky coincidence, Lyell’s comment about the “economy of nature” holds up for a large part of geological history. However, he had no reason at the time to assume that this should be the case.

Trying to solve a puzzle with half the pieces

Many ideas in Principles of Geology still hold up today, but with the benefit of hindsight, a modern reader can identify some absolute clangers. However, nothing can be gained from pointing and laughing at the ignorance of our predecessors. Principles of Geology is a work in progress from someone trying to solve a puzzle with only half the pieces – without realising that half the pieces are missing.

Reading this book makes you question your own certainty, and ponder the rigor of your own interpretations. You might think that you have enough pieces to cobble a picture together, but there’s no telling when the next Alfred Wegener will come along to inform you that you’ve been looking at everything wrong the whole time. And wouldn’t you be reluctant to pull apart your work and start again, if you had spent so long on it? It takes strength to admit that you have wasted time barking up the wrong tree.

Objectivity becomes challenging when observation and inference get tied up with pride and intellectual ownership. Looking back at Lyell’s work, this is easy to see – but we shouldn’t forget that the same battles are raging today. Scientific advancement is a matter of convincing others, rather than stumbling upon an objective truth. Findings only become facts through consensus – so what do we know, really? What is knowledge, and what is progress? Something to ponder, if you have as much spare time as a Victorian gentleman…

Is the present the key to the past?

Yes and no. We now know that the land beneath our feet wasn’t always at the same position, and that the global climate and atmospheric composition have changed significantly over millions of years. But the laws of physics have probably been constant since before our planet formed, and these have the ultimate control over all Earth processes, moving, morphing and melting its rocks. Still, although we can use our present surroundings to learn about past events, there is no reason to assume that conditions have always been exactly the same. Lyell’s mantra is sometimes useful, but it is not always useful.

In summary…

I hope you have enjoyed this dive into old science. Actually, this book reminded me how young the geological sciences are. We knew more about stars, radioactive decay and special relativity before we had a clue about the processes governing our own planet.

Hopefully this hasn’t triggered an existential breakdown…. It’s healthy to question your perception of reality now and then, right? If humanity lasts another 200 years, science might end up looking completely different. Which of our firmly-held beliefs will one day be labelled as absolute clangers? It’s impossible to know. So, good luck to all you science fiction writers out there, if you’re aiming for realism. Happy reading, and have a lovely week!

Oh – and come back for part two. It has dinosaurs and volcanoes in it.