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If you don't know about Polymoth Books, click here.

I wish to announce a rather crazy scheme on my part: a package of 22 of the best books I have written this century, all curated and presented as DRM-free PDF files. Librarians just need to email me at petermacinnis44@gmail.com.

Note that all of the books are available as Kindle e-books and Amazon Print-on-demand books as well (but I can do mates rates).

The main aim of this PDF scheme is to set my intellectual property loose in schools. Teacher-librarians will be allowed to make class sets of any book (or books), for one term, once they have paid a one-off fee of AUD$50 for the collection, on either a CD-ROM or a USB stick. That includes postage and GST, but you need to order, get an invoice and pay first.

At the end of the term, I ask that TLs delete the files from devices, but if they wish, they can immediately copy them again. I rely on the ethics of TLs, and won't be checking. I also have no plan to check the credentials of purchasers, and will declare all such to be honorary teacher-librarians. My aim is to influence minds, not to make money, so if you fulfil any TL-like role, that's good enough for me. Ordinary librarians count as well, and friends are welcome.

Some of the books in this scheme came out through mainstream publishers and some of them won awards, but were allowed to lapse by lazy publishers, others were excellent ideas that nervous publishers shied away from. All have been seized back, meticulously curated and brought up to date. It has to be conceded that small portions of text (and some illustrations) may appear in more than one volume, because there are certain themes I harp on.

Any good educator does exactly that, repeating the key points.

As you can read on a link that I will post by the end of the month, this century, my work has been awarded:

• Seven CBCA long listings (notables), two CBCA short listings, one Honour Book and one Book of the Year;
• One Short Listing in the NSW Premier's History Awards, Young People's History Prize ;
• Two Australian Awards for Excellence in Educational Publishing;
• One WA Premier's Book Award for Children's Literature;
• One international White Ravens List entry (Germany);
• One Wilderness Society Short List entry, and
• Two Whitley awards.

In other words, there's some serious intellectual merit here.

The titles involved are: 

Australia's Hidden Heroes; sample here

Australia's Pioneers Heroes and Fools; a sort of sample here

Australian Backyard Explorer; sample here

Australian Backyard Naturalist; sample here

Curious Minds; sort of sample here

Kokoda Track: 101 Days; sample here

Looking at Small Things; sample here

Mistaken for Granite; sample here

The Monster Maintenance Manual; sample here

Mr Darwin's Incredible Shrinking World; sample here

Nature of North Head; sample here

Not Your Usual Bushrangers; sample here

Not Your Usual Clever Ideas; sample here

Not Your Usual Gold Stories; sample here

Not Your Usual Treatments; sample here

Not Your Usual Villains; sample here

Old Grandpa's Book of Practical Poems; sort of sample here

Playwiths; sample here

The Lawn a Social History; sample here

The Speed of Nearly Everything; sample here

They Saw The Difference;  (sample) and 

You Missed a Bit. Typical example

I already have a marketing operation in place, and dead-tree versions of all of these books (and also individual e-books with DRM) are available from Polymoth Books, and you can find out about the contents of each title through that link.

I will, in the near future, be providing sample chapters or excerpts through this blog, each bearing the title of the book they come from.

Now, if you'll excuse me, I have some files to sort.

Oersted's experiment

 This is from a book I am about to start pitching:

Hans Oersted is remembered in the name of the unit of magnetic field strength, the oersted. He was also the person who coined the term ‘electromagnetic’. With that sort of introduction, it should not be hard to work out that it was Oersted who first observed the magnetic effect of an electric current. All the same, Oersted was trained in metaphysics (a branch of philosophy), rather than in physics.

Nonetheless, in 1806, he became professor of physics and chemistry at Copenhagen. As well as being the first to prepare metallic aluminium, Oersted is remembered for his discovery of electromagnetism, which he made during a lecture. His discovery of the electromagnetic effect was immediately translated into several languages, though not entirely reliably. The 1826 English source I found for his work contained a contradiction which was not in the 1820 French version I happened to have to hand, so my quotation below is a mix of the two versions.

If he had written in Latin, and we had all been forced to learn Latin, this problem would not have arisen, but even by the 1820s, Latin was no longer universally understood.

The first experiments…were set on foot in the classes for electricity, galvanism and magnetism, which were held by me in the winter just past. By these experiments it seemed…that the magnetic needle was moved from its position by the help of the galvanic apparatus…when the galvanic circuit was closed, but not when open, as certain very celebrated physicists in vain attempted several years ago…

A modern re-enactment of Oersted’s experiment. My choice of the aluminium ruler was deliberate.

You can see the way this worked in the illustration above, but as this is simple enough for the reader to try, let me note that the entire apparatus is one compass, one AA cell, a length of insulated wire and some sticky tape, plus an aluminium ruler which is optional, but it would have pleased Oersted. I bared one end of the wire, taped it to one end of the dry cell (this was sloppy practice but good enough) and bared the other end.

I taped the dry cell to the ruler (or to the rule if you are a pedant), taped the compass to the ruler to stabilise it, and that was it. As you can see, a single dry cell was enough to bring about a noticeable swing. Incidentally, if you reverse the wire (and as a result, the current), the swing reverses, and the same reversal happens if the wire is under the compass.

One of the great continuing arguments in science relates to the need to justify research in advance, usually for the benefit of bean counters, weasels and other parasites, by showing what research is useful for. Even the most useless-looking piece of science can become useful, as Karl Pearson was to discover. Here, Lord Kelvin reflects upon Oersted’s researches:

Oersted would never have made his great discovery of the action of galvanic currents on magnets had he stopped in his researches to consider in what manner they could possibly be turned to practical account; and so we would not now be able to boast of the wonders done by the electric telegraphs. Indeed, no great law in Natural Philosophy has ever been discovered for its practical implications, but the instances are innumerable of investigations apparently quite useless in this narrow sense of the word which have led to the most valuable results.
—Lord Kelvin (1824–1907), 1846, quoted R. A. Gregory, Discovery (1916), 241.

Aside from Luigi Galvani and Alessandro Volta, the main players in the unravelling of Faraday’s electromagnetism include Georg Ohm, Hans Oersted, and James Clerk Maxwell, who brought us to the point where we could see light as an electromagnetic wave, much as Michael Faraday had expected, leading on to George FitzGerald, and then to Heinrich Hertz, Guglielmo Marconi and beyond.

There are also the users of electricity and magnetism, from Joseph Henry and Edward Davy, who both invented an electric relay, Charles Wheatstone, Alexander Graham Bell, and people like Joseph Swan, Thomas Edison and Nikola Tesla who made our modern uses of electricity possible.

There was far more to magnetism than compasses for navigation. After Oersted found that a variable current in a wire would make a compass needle deflect from its usual direction, André Marie Ampère (1775–1836), found that like currents attract, then he discovered the solenoid in 1826: this was a coil of insulated wire with a current passing through it, and it would be the basis of transformers, electric motors, relays and electromagnets. The most common and audible household use of the solenoid today is probably in the switching systems which commonly turn the water flow on and off in washing machines.

Ampère completed his work while believing incorrectly in two ‘magnetic fluids’, which he called a northern fluid, and a southern fluid. So long as he observed correctly, and so long as his theory allowed him to make sensible predictions to test, it mattered little. Then in 1831, Michael Faraday discovered electromagnetic induction, and soon after, invented the very first electric motors.

Following on from this in 1845, Faraday discovered what we now call the Faraday effect, where a magnetic field makes the plane of polarised light rotate. This later influenced James Clerk Maxwell to come up with the idea of electromagnetic radiation, which led to Hertz inventing radio. And it all came from one simple observation by Oersted, a lifetime earlier!

Science is like that…

And that, by the way, is my preferred name for the book.

Benham's colourful tops.

 Charles E. Benham (1860-1929) was a journalist and inventor, and he deserves more than this, or what his Wikipedia entry, offers. I was triggered to go here this morning because of a comment Stew made about my last entry: there may be more, later.

When I first discovered the Benham disc, I was delighted, because I am colour-blind. The Benham disc is a black and white patterned circle, which looks coloured when it is spun around. I had heard of these things but I had never tried them, and I thought it would be interesting to see whether they had the same effect on a colour-blind viewer. Being colour-blind does not mean that you “see everything in black and white”, as David Brewster said. It simply means you see colours differently. It occurred to me to wonder if maybe I would see different colours in the disc from those other people see.

Benham described his illusion in an article published in Nature  back in 1894. In those days, if you wanted to see the disc, you would look for the design on a children’s top, known, predictably, as ‘Benham’s top’. The first account was a brief and anonymous one, noting that the ‘disc’ on the top was a black semi-circle, with the white half of the circle divided in four, and with black arcs painted in.

As the disc is rotated, people see different colours from the different black arcs. And, as the reporter noted, if “. . the direction of rotation is reversed, the order of these tints is also reversed. The cause of these appearances does not appear to have been exactly worked out.”

An ‘Artificial Spectrum Top’, devised by Mr. C. E. Benham, and sold by Messrs Newton and Co., furnishes an interesting phenomenon to students of physiological optics. The top consist of a disc, one half of which is black, while the other half has twelve concentric circles drawn upon it. Each arc subtends an angle of forty-five degrees. In the first quadrant there are three such concentric arcs, in the next three more, and so on; the only difference being that the arcs are parts of circles of which the radii increase in arithmetic progression. Each quadrant thus contains a group of arcs differing in length from those of the other quadrants. The curious point is that when this disc is revolved, the impression of different colours is produced upon the retina.

(Nature , 51 (1309), November 29, 1894, 113–114.)

There followed an animated correspondence, during which Benham stepped in. Illuminate the top with a bright sodium flame, he said, and you will see a very clear blue, and a very clear red. And now the controversy heats up: immediately underneath, in the same issue, Professor Liveing retorts that he has seen no such colours: the phenomenon is obviously a subjective one. Clearly there is room for more research here.

It is unclear whether Nature  thought so too, for they go on in the same column to publish next a letter from F. G. Donnan in Leipzig, suggesting that we need a new word in chemistry: ‘solute’, and the discussion seems to have died there. Well, as far as I can judge, I see the same colour effects as other people, which means we won’t learn anything about colour blindness from the Benham disc. But how about trying to learn about colour vision? What causes the colour effect as the disc slows down?

Most explanations seem to speculate rather than to explain, but here is the official version as found in psychology text-books. We have three kinds of light receptor in our eyes, in the same way there are three kinds of phosphor in a colour TV. Speaking crudely, these receptors, the cone cells, are all sensitive to just one of red, green and blue.

According to the theory, you need all three kinds of cone in the retina of your eye to see colours normally. Somehow, the cones which pick up one of the colours (red, for example) must react differently to flashing lights of a particular frequency. So with different size black bits on the disc, we get different frequency effects, and so our eyes are stimulated to ‘see’ different colours.

Well, that’s what the theory says. Some time in the future, a careful and critical look at it, will reveal once and for all whether and how this official explanation operates, and where it breaks down. There is probably a Nobel Prize in this for somebody, though they will need to acknowledge Gustav Fechner, and that's a hint.

Making predictions

Yes, it's been a bigger time gap than most, because in Covid-19 time, I have been clearing my back burner of partly done books. More of the current time-stealer in the near future.

* * * * * * * * * * * * * * * * * * * * * * *

Out there, somewhere, there is a discovery, an observation, a measurement that does not quite fit the present model for something. There is an idea, a notion, a hunch that will some day become a great discovery of science. I have no idea how long it will take for us to realise that it is both a discovery and a great discovery, but it will occur to us one day that we ought to have seen it coming.

I have no intention of trying to predict what it might be, because as Niels Bohr used to say, making predictions is problematical, especially about the future. Bohr always said he got it from Robert Storm Petersen, who apparently got it from somebody else.

Some people out there will already have predicted it: in 1906, rocket scientist Robert Goddard was thinking of the energy in a gram of radium and wondering if it could be used to power a rocket. In 1913, H. G. Wells was describing the dropping of an atom bomb, though he thought the target would be Berlin. Nobody paid attention.

Most predictions miss the mark. For the past hundred years, every depiction of the future has offered us food pills, flying cars and easy access to space, and none of those has happened.

Then again, remember Arthur C. Clarke’s First Law: When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.

They say Thomas Watson, chairman of IBM, said in 1943: “I think there is a world market for maybe five computers.”

who could have guessed that two World War II developments, jet engines and computers, would lead to us booking our overseas holidays online in the 21st century?

When scientists get old, they often become fixed in their ways. They make dogmatic statements, and expect everybody to accept what they say, but more often than not, they turn out to be disastrously wrong. Take these examples:

• In 1797, farmers in America rejected a new cast-iron plough, saying it would stimulate weeds and poison the crops.

• The patent for the radio valve (the thermionic valve, the thing we used before the invention of the transistor) was not renewed when it ran out in 1907. Nobody could find a use for the Edison effect until a few years later.

• During World War II (when the first atom bombs were exploded), an admiral reassured the American vice-president: “Atomic bombs won’t go off, and I speak as an explosives expert.” (Even though H. G. Wells had predicted atomic bombs in his novel The World Set Free, as early as 1913!)

• A few years earlier, Ernest Rutherford, New Zealand’s greatest scientist, and one of the greatest scientists of this century, said “The energy produced by breaking down the atom is a poor kind of a thing. Anyone who expects a source of power from transformation of these atoms is talking moonshine.”

• Twelve years before the first moon landing, and just after the first Russian satellite was launched, the Astronomer Royal of Great Britain commented that generations would pass before people landed on the moon, and even if they did, there was little chance they would ever get back to earth. (In fairness, the Astronomer Royal was being political, as funds were being diverted into rocketry that he thought should have been going to astronomy.)

The moral of this list of disasters: keep an open mind, because things may change sooner than you think. And if you have to make a prediction, try to make sure nobody writes it down! But if you want to see science flourish, don’t let such fears stop you from making or drawing inferences.

What geologists think, part 3

8. The standard principles of science

These are ideas that all scientists just assume, but they are rarely stated explicitly for students or the public. There is enough information here to tell you what each idea is about, and you will find enough terms to let you look the idea up, if you need to. There are lots of ins and outs, and working scientists spend their lives mastering them. They will, I hope, recognise that this is Science Lite.

Atoms and molecules

All matter is made up of atoms, and the properties of any piece of matter will depend on what atoms are present, and how they are arranged and connected. Many atoms join up to form regular frameworks that we call crystals. Sometimes, atoms join into tight standard groups, like water, quartz, salt and sugar. We csll these groups molecules.

The laws of thermodynamics

For general purposes, heat flows from hot to cold, perpetual motion is impossible, and there is no such thing as a free lunch. By the way, if you want to drive a politician or an arts administrator to distraction, ask him or her to explain (or even just to state) the second law of thermodynamics. Trust me: it matters!

A good many times I have been present at gatherings of people who, by the standards of the traditional culture, are thought highly educated and who have with considerable gusto been expressing their incredulity at the illiteracy of scientists. Once or twice I have been provoked and have asked the company how many of them could describe the Second Law of Thermodynamics. The response was cold: it was also negative. Yet I was asking something which is the scientific equivalent of: Have you read a work of Shakespeare’s?
—C. P. Snow, Rede Lecture The Two Cultures and the Scientific Revolution (1959).

 If you want a simple version, it says that differences in temperature, pressure, and density tend to even out, after a while. More detailed discussion involves entropy The simplest available version of that: entropy is a thermodynamic function that measures randomness or disorder. If you like, entropy is a measure of untidiness.

 

Most of the principles of science are what scientists call counter-intuitive. In lay terms, they seem to go against our gut reaction; the earth as we experience it looks flat, and our intuition tells us the sun and moon circle around us once a day, but ignoring intuition, all scientists agree that the world is a globe, we orbit around the sun, and the moon orbits around us once a month.

Entropy is slippery, rather than counter-intuitive, and you have to note the qualifications which limit entropy to inside a closed system. Under those conditions, entropy, or disorder, increases, which is how scientists say that over time, everything gets more random, more dispersed.

There can be no exceptions to the rule that entropy, the disorder of things, always increases, but life, at a local level, can be an anti-entropy agent, making some things more ordered at a local level, even as entropy is increasing on a larger scale. In simple terms, animals and plants gather up and concentrate certain elements in our bodies.

Across the universe, every change leads to an increase in the total entropy, but the delight lies in the details, and a lot of geological science comes down to explaining how, on a local level, the process of concentration in elements or minerals is driven.

If [your pet theory of the universe] is found to be contradicted by observation—well, these experimentalists do bungle things sometimes. But if your theory is found to be against the second law of thermodynamics I can give you no hope; there is nothing for it but to collapse in deepest humiliation.
—Sir Arthur Stanley Eddington, The Nature of the Physical World (1928), chapter 4.

Conservation of mass and energy

In simple terms, matter and energy can neither be created nor destroyed. There is No Such Thing As A Free Lunch.

Equilibrium

As a rule, things are in balance, but that is not the same as saying they are unchanging. The number of oxygen molecules in an open jar may vary slightly over time, as molecules whizz in and out, but at any practical level, the entries and exits cancel each other out. If I have crystals of salt sitting in a saturated brine solution, some of the chloride and sodium ions in solution may attach to the crystals, but on average, just as many ions will leave the crystals. We say the solid and the solution are in dynamic equilibrium.

The law of large numbers

There is no such law, but it is convenient to pretend that it exists. Given time, every atom of a sample of radioactive carbon-14 will break down. We cannot say when a given atom will decay, but with large numbers of atoms, we can say that half of all of the atoms that we start with now will have decayed if we come back in 5730 years from now. We say that carbon-14 has a half-life of 5730 years.

Evolution

Evolution also hangs on large numbers. You won’t evolve, I won’t evolve, but our species, like every other species, does evolve. Don’t worry: some of your genes will carry forward, and some of them may be more common in a future population.

(I anticipate, for example, that in a thousand years, the descendants of today’s Australians will have a skin color darker than mine, due to the selective effects of melanoma.)

(Note that this can  be negated because humans, uniquely in an evolving world, can apply social changes to limit selection effects.)

Falsifiability

Every part of science is able to be falsified by evidence, and if some idea can’t be tested and potentially falsified, it just isn’t science. That doesn’t mean science is all false, it just means every assumption is always considered open to testing and being found wrong.

If we found dinosaur fossil bones and human fossil bones in the same rock, this would mean we probably had to revise large parts of what we think we know about geology and biology, though the first step would be to check carefully that somebody hadn’t just pulled off a hoax.

Scientists are always on the alert for contradictions like that, even though they don’t really expect to find any. One way to become a famous scientist is by finding a red-hot contradiction to what everybody believes.

Ockham’s Razor

Then again, maybe we wouldn’t need to revise anything. William of Ockham made it a lot more complicated, but his basic notion was that if there are two possibilities, you should take the simpler one. If we found human and dinosaur fossils in a single rock, a simpler explanation would be fraud. We would at least look for evidence of fraud first, but if there was truly no evidence of fraud, it might be time to start a rethink.

9. Caveats

I am not a geologist, but I know how to think, where to look, and what questions to ask. My undergraduate studies were mainly in the areas of botany and zoology, so I may, from time to time, be in error. As a professional science writer, I am used to checking my facts, but even when I get the latest opinions there is still one gotcha remaining.

Science changes, and geological science does change—and I saw it happen. When I was an undergraduate, I picked up one year of formal geology training, enough to appreciate that the rocks yield the soil that my precious plants flourish in, plants that feed my equally precious animals.

One day, one of our geology lecturers urged us to attend certain sessions of ANZAAS, the Australian and New Zealand Association for the Advancement of Science. “Listen to Sam Carey,” he told us. “He’s quite mad: he thinks the continents are moving.”

That was in 1962, and I did indeed hear Sam Carey talking about such wild ideas. He seemed to make a reasonable case, except that we all knew the idea was crazy. Just three years later, plate tectonics was all the go.

In fairness, Sam Carey was only partly right, because his notion was based on some false assumptions, but the key thing to note is this: in 1962, moving continents was madness, by 1965, it was pretty much the orthodox model.

I have tried in this book to stay with the best and safest bits of orthodoxy, but at any time, that which was orthodox can be defeated of overturned by a simple paradox. One new discovery is all it takes, as T. H. Huxley said while discussing historical work on the spontaneous generation of life:

But the great tragedy of science—the slaying of a beautiful hypothesis by an ugly fact—which is so constantly being enacted under the eyes of philosophers, was played almost immediately, for the benefit of Buffon and Needham.
—T. H. Huxley, Presidential address to the British Association in September, 1870.

My book (meaning Not Your Usual Rocks, still to be published) is about the facts—though I will later discuss a maverick theory about the origins of oil. I don’t believe it, but it is both entertaining, and instructive to consider as a way of seeing how science works.

By the time you are done, all of these will make perfect sense.

What geologists think, part 2.

As I said before, I'm cleaning up all the unfinished projects, and Not Your Usual Rocks is at the top of the pile.

You'd probably be better off starting with Part 1, but there are two by-the-ways

1. The photos that aren't credited are mine, and they are all
© Peter Macinnis, Creative Commons Attribution 4.0 International.
That means you can use them for non-commercial purposes with attribution, but while I squash thieves like the people at the Charles Sturt Memorial Museum, I will happily provide high-res copies to people who ask.

2. The locations reflect a lot of travel, but you can probably work out roughly where I live, if you live near me. If you do, say g'day!

6. All of the effects we see in the geology can be explained

Basically, all the things that we see in the world can be explained by the forces we see operating today. Geologists call this principle uniformitarianism, and it just means the natural laws and processes that we see shaping the earth today are the same ones that shaped the past.

In other words, we don’t work on the principle that there used to be wizards and witches who moved the rocks around; there were no fire-breathing dragons that made the lava melt. We do not need to assume the existence of pixies driving Stealth Bulldozers, poltergeists with geological interests, malignant mammoths, whimsical aliens or lost civilisations.

Continents move, floating on the surface of the planet; earthquakes happen; rocks form, weather and erode; rocks get pushed up; others get pushed down and buried, and so on. On a smaller scale, sediments get washed by water, blown by winds, and sometimes, pushed by glaciers.

When weight is applied to the existing surface, in the form of glaciers or any other way, the earth’s crust behaves like a small raft that an elephant has boarded: the rocks sink. On the other hand, when glaciers melt, the earth springs back up again, and this is currently happening in Scandinavia which was relieved of a lot of weight, about 10,000 years ago.

The rocks, even the not-your-usual rocks, keep to the following principles.

7. There are standard rules of geology

Sometimes, what you see may appear to be contrary to these rules, but if you think that, it usually means you haven’t thought hard enough. The apparent contradictions emerge only because you are unaware of the other rules that applied in a particular place. With enough thinking, you can generally explain what you see.

Rocks are usually laid down in flat layers.

It is a fairly safe rule that sedimentary rocks form flat, parallel beds, because the sediments are washed or blown into some sort of basin, and the first material fills in the gaps and crevices, leaving a flat surface. The effects of currents (or winds) and gravity keep the top fairly flat.

Horizontal strata, Bungle Bungles, Western Australia

An illustration from Charles Lyell’s The Student’s Elements of Geology (1871), page 17, showing how irregularities in an underlying surface are filled in, slightly contradicting Steno. [Public domain]

Then again, some beds can be laid down on a slope. This is called cross bedding or current bedding, and we will look at it in more detail later. Cross bedding can be distinguished from beds that have been tilted later by looking at the horizontal beds above and below.

 

Cross bedding in Hawkesbury sandstone, Old Man’s Hat, North Head, Sydney, Australia

There can be traps for the unwary when it comes to igneous rocks. If the rock arrives as lava, streaming down the flank of a volcano, some of the lava cools and becomes solid, leaving a sloping skin of rock. Nothing is inexplicable.

Eroded remnants of an old volcano near Cape Palliser, North Island, New Zealand.

Younger rocks usually lie on top of older ones

They are always laid down that way, but there are a couple of notable exceptions. Basalt sometimes pushes up through sedimentary (or other) rocks to form a dyke. If the dyke reaches the surface, it flows out over the landscape (which is why it is called a flow. A flow is always younger than the rocks it lies on top of, and older than any rocks which are found above it.

Sometimes, the basalt pushes in between two layer of rock, forming what is called a sill, but the basalt remains younger than the rocks that lie on top of it. How do we know? We look for contact metamorphism, above and below.

The other exception to youngest-on-top comes when rocks bend, and fold, and sometimes (rarely), overfold, so that the usual age order is reversed in a limited area.

In less extreme cases, horizontal beds may just be tilted up and eroded away, leaving tilted rocks behind. If the land sinks at this point, new sediments wash in to start a new age of rock building.

In an area where there are active volcanoes, lava may pour out and flow across the countryside, laying fairly flat layers—except, as mentioned above, on the flanks of the volcanoes, where sloping beds will form.

The Columbia River forms the border between Washington and Oregon in the USA, flowing through a valley carved through a massive series of basalt flows.

  

There can be gaps in the geological record in any place

On my home territory, near Sydney on Australia’s east coast, the rocks are Triassic in age. If you drill straight down you will come eventually to Permian rocks, the coal measures that are exposed around the margins of what we call the Sydney Basin. You find coal at Newcastle, Wollongong, Lithgow and other places. Coal also used to be mined on the very shores of Sydney harbour, but they had to sink a shaft quite a long way down, all the way to the Permian rocks.

In theory, if we keep going down, we should next move into rocks from the Carboniferous, but these layers are missing in my favourite walking area, in the Budawang Ranges, west of Nowra, south of Sydney. We meet up with tilted Devonian metamorphic rocks instead. It looks as though we are missing 100 million years (or more) of geological history.

Any rock-hound will tell you this is an unconformity, and hazard a guess that the Devonian rocks were deeply buried and covered with Carboniferous rocks, but that the earth and its rocks moved hugely, and any Carboniferous rock was eroded away, leaving ribs of tough Devonian stone across the land in the early Permian era. We really can’t be sure there were ever any Carboniferous rocks, but it is quite likely that they came and went, leaving no trace.

Later, the land all sank deep into a sea of some sort of cataclysm. In the Budawang ranges, the lowest layer of the Permian rocks is a conglomerate containing very large boulders, telling us that the first deposits in that part of the basin were laid down in a huge flood.

At Myrtle Beach, on the south coast of NSW, this conglomerate layer is missing, suggesting that the oldest Permian sediments there were laid down at a different time. It may have been a few years, more probably it was a few millennia—or even quite a few millennia. Geology never scurries.

Myrtle Beach, south coast of NSW. The sloping beds below are pointing to 1 o’clock,

and the hand (top left) spans a gap of about 100 million years in the geological record.

There is also a simpler sort of time gap, much harder to identify, called a disconformity. This happens when sediments stop being delivered for a while, but we can largely ignore these hiccups for the moment. We now have the basic background to understand a bit of slightly more detailed geological history. 

The laws and principles of geology

Nicolas Steno started it. Here is a modern version that conveys his thinking in the language we use today.

* Steno’s Law of Superposition says that in a sequence of strata, any stratum is younger than the sequence of strata on which it rests, and is older than the strata that rest upon it.

* Steno’s Law of Original Horizontality says that strata are deposited horizontally and then deformed to various attitudes later. That is, undisturbed true bedding planes are nearly horizontal, though we need to note here that cross-bedding is possible where sandhills or sandbanks are being formed.

* Steno’s Principle of Lateral Continuity: strata initially extend sideways in all directions. That is, every outcrop in which the edges of strata are exposed demands an explanation, and strata on two sides of a valley represent erosion of the rock between.

* Steno’s Principle of Cross-cutting Relationships: anything that cuts across layers post-dates them. This applies particularly to igneous intrusions such as dykes. Aside from Steno’s principles, geologists accept the following notions:

(1) an intruding rock is younger than the rock it intrudes into;

(2) a fault is younger than the rock which is faulted;

(3) any pieces of ‘foreign’ rock included within a rock must be older than the rock they are found in; and

(4) William Smith’s principle of fossil succession.

We will come to that in a moment, but geology was only possible because of James Hutton. He had made enough money from an ammonium chloride factory to be able to retire from work and study geology.

Hutton was an old friend of Joseph Black, the first scientist to distinguish heat from temperature, and also of James Watt (the steam engine maker), so it is no surprise to discover that Hutton assumed that all earth activity was due to what he called the earth’s ‘heat engine’. But most importantly, he said that “…The past history of our globe must be explained by what can be seen to be happening now”.

He emphasised the igneous origin of many rocks (unsurprisingly, given that he came from Edinburgh, where igneous rocks rear up all around the town). Unfortunately, the French Revolution was happening, so the public in Britain was less than enthusiastic about Hutton’s revolutionary notions. They were not only unready for his ideas, they were unwilling to accept them, but the scene was now set.

John Playfair was probably one of the few people to combine geometry with geography and geology. Trained in mathematics at a time when geology had not yet been invented, Playfair was necessarily largely self-taught. Like James Hutton, Playfair was exposed to the stimulating geology of Edinburgh, which would have assisted him in his work.

He also invented geomorphology, giving us ‘Playfair’s Law’, which states that rivers cut their own valleys. Then he gave us the modern concept of grade when he asserted that the angle of slope of each river shows an adjustment towards a balance between the velocity and discharge of water on one hand, and the amount of material carried on the other.

Playfair also made the work of Hutton more accessible when he published his Illustrations of the Huttonian Theory of the Earth in 1802. He explained the rock cycle of repeated weathering, erosion, deposition and solidification in simple terms: notice, with a modern eye, how he covers weathering, erosion, sedimentary rocks forming in the sea and uplift.

The series of changes which fossil bodies are destined to undergo, does not cease with their elevation above the level of the sea; it assumes, however, a new direction, and from the moment that they are raised to the surface, is constantly exerted in reducing them again under the dominion of the ocean. The solidity is now destroyed which was once acquired in the bowels of the earth; and as the bottom of the sea is the great laboratory where loose materials are mineralized and formed into stone, the atmosphere is the region where stones are decomposed, and again resolved into earth.
—John Playfair, Illustrations of the Huttonian Theory of the Earth, 1802, 109.

The idea of igneous rocks came later. Playfair’s ideas only gained wide acceptance after Charles Lyell added Playfair’s ideas into his Principles of Geology, but we have left out William Smith, an orphan who was set to work early as a surveyor for the new canals that were beginning to cross the British countryside, so industrialists could haul goods from place to place.

 

These canals required digging into the ground, and they had to cut tunnels through hillsides. This all gave Smith first-hand chances to observe and classify the many rock types as they are seen in fresh unweathered exposures. Most importantly, he noticed how strata were typified by fossils, and he pointed out that the same stratum could be identified at a considerable distance by the fossils it contained.

In 1816, Smith published his ideas, accompanied by a coloured geological map, and made the point that, given the law of superposition, the fossils in the strata gave us a view of the history of life on earth. Now the way was fully prepared, and Charles Lyell’s Principles of Geology could be released in the early 1830s, just in time for Charles Darwin to take them with him on the voyage of HMS Beagle. That meant he was prepared to unravel in full detail the reasons why life actually possessed a history on earth.

That is how science weaves itself into a web, but it also involves cycles.

Geological science is also science, and there are some principles of science, as well. I will get to those in part 3.