Ant lions

Ants are a necessity we fail to appreciate.  They clean up our gardens, disposing of dead things keeping the garden sweet-smelling.  Ants are generally hard to see, so people often ignore their usefulness.  When they show up around picnics, we resent them, if they get into the house, we hate them, and when they sting us, we loathe them.  Small wonder, then, that most Australian children love the ant lion.

The ant lions are not a tall tale.  They are small predatory insects, the larval stages of lacewings, which prey on ants.  In their adult stages, some lacewings are said to eat aphids, so they are highly regarded by even the most ant-loving adults, or at least those few who know them.

There are ant lions all around the world, but we seem to have more of them in Australia.  The larval ant-lion digs a pit of great cunning, and lurks at the bottom, waiting for an ant to tumble down to its lair.  Once there, the ant will be seized in the ant lion's terrible pincer jaws, and sucked dry.  To do this effectively, the ant lion uses a rather handy little principle of engineering.

Pile some dry sand upon a table, and it will form a cone of a very predictable shape.  Dry sand has a typical ‘angle of rest’, about 30.5 degrees from the horizontal, if the grains are perfectly spherical.  If you shovel dry sand back over your head, you will dig a hole that will slowly get deeper.  If the slope of the sides becomes steeper than the angle of rest, some sand will roll down, making your hole broader and shallower, until the angle of rest is achieved, all around the edges.

If the slope is less than the angle of rest, you can go on deepening your hole until the angle of rest is exceeded.  In the end, either way, you get a beautifully symmetrical conical depression with dry sandy sides, all poised to fall away at the lightest tread.  The ant lion uses its large head like a flicking shovel.

It burrows backwards into the sand, and then flicks the dry grains up and away.  Some fall back into the hole, but soon there is a conical depression which grows until the trap is some 2 cm across.  Then the ant lion digs in at the bottom, with only its pincers in view, waiting for dinner to slide into reach.

An ant, blundering over the edge, starts to slip down the side, dislodging a small avalanche of sand grains as it goes.  This is no problem for the ant, this sort of thing happens all the time in sandy soil.  It starts to scramble laboriously up the slope.  As it goes, it casts more sand down, but slowly it creeps up towards the rim and safety.

But at the bottom of the pit, the ant lion feels the patter of the falling grains, and begins furiously casting sand out of the hole in all directions.  This deepens the hole and undermines the struggling ant from below, and some of the falling grains help to tumble it back down from above.  Occasionally, an ant escapes, but mostly, they fall to the bottom where they are seized and reduced to a husk.  This dried shell is later cast out of the pit with a single toss of the ant lion's powerful head.

Children who have been bitten by ants delight in dropping their tormentors' relatives into the pits of wild or captive ant lions.  In the past, I have collected a wide range of other small insects, and found that ant lions are eclectic diners.  They only eat ants because ants are so much more freely available.  A small weevil, a small sand hopper, even a spider will be dragged down and consumed if it strays within reach.

Ant lions are found wherever there is sandy soil, especially where it is protected from direct rain: under rock ledges, in hollow trees, beside fallen logs, close to buildings, and under any buildings which are on raised piers, a common Australian architectural form.  In really sandy soil, they may even cover open ground with neatly spaced traps.  

All you need to keep ant lions.

The ant populations around our house are increasing now to the highs of high summer, and the ant lion numbers are building up as well.  In a few weeks, I shall catch half a dozen, and take them to school in an ice cream container of sandy soil.  I can think of few better animals to use when introducing students to the hidden world of small insects.  After all, a system is a system, wherever you find it . . .

Sandstone thoughts

South Head/Eastern Suburbs, Sydney

Sydney is a sandstone city.  We have cappings of shale here and there, and if you dig deep enough, you will find coal below the sandstone, but looking at the surface, looking at the hills and the headlands, Sydney is undoubtedly a quartz-rich sandstone city.  Quartz is silica, silicon dioxide to the chemists.  Silica is a very common mineral, dirt common, even.  By itself or in combination, silica makes up more than 50% of the planet earth.  Sand is silica, flint is silica, even granite is mainly silica or silicates.

Cliff and rock platform, South Head

Yet quartz is also a most uncommon mineral.  You can scratch the toughest steel with a piece of ordinary glass, you can scratch the toughest glass with quartz, but very few things will scratch quartz.  Quartz is uncommonly hard.  This combination of the common and the uncommon explains why sandstone is so easy to find, all over the world.  As sun, wind, frost, snow and water all worry away at the rocks, some minerals break down to clays and salts, but quartz grains stay as they are.  As the other minerals fall apart under the stress of the weather, quartz grains just fall to the ground and join the soil.

As the soils blow around, softer minerals are crushed to dust, but silica grains just get less angular as they rattle against each other.  Acids in the soil destroy other minerals, but the quartz grains just lie there, inert and uncaring.  When a flood washes soil in a raging torrent down to the sea, the quartz grains may crack until they are too small to be affected by any further pounding.  After that, they just roll along, getting a little bit rounder, still silicon dioxide, unchanged and unchanging.

Sand travels till it reaches the sea, where some grains wash up on the seashore.  They get rounder still, as they roll and pound along our beaches, but still they do not change.  Chemically the sand is still quartz, uncommonly tough, and incredibly common.

Bedding, Lion Island, Broken Bay

Bury these sand grains under a kilometre of sediment, and they will settle a bit closer together.  Give the buried sand long enough, and a few atoms will wander and fall into a new place, linking two grains together, bridging the gaps.  If water soaks through the sand, crystals of dissolved minerals may form in the crevices, locking grains together.  In time, the sand becomes sandstone, waiting deep within the earth for erosion to uncover it once more.

But sandstone is not as tough as pure quartz.  The fragile bonds between the grains can be broken, the minerals in between can dissolve out, and the grains can be wedged off, one by one, just as soon as the weather reaches the stone, within a few metres of the surface.  In time, weathering will shape the sandstone into new and marvellous shapes.

Pure silicon means big money to the techno-whizz kids in Silicon Valley.  They ‘dope’ their pure silicon with a few impurities, tiny amounts of other elements, just enough to make their valuable pure silicon truly wonderful.  Traces of impurities are just as important in the sandstone.  A few bits of plant stems or leaves, or a tiny dead animal, are all the impurities you need to get started, along with a bit of rust .

In some simple chemistry, the rust is reduced to soluble ferrous iron which drifts slowly through the rock until it is oxidised again to ferric iron.  This chemistry makes spheres of tough iron-rich stone, waiting deep inside the sandstone.  Uncovered, they make fantastic patterns in the stone, for the spheres will eventually be revealed as complex rings and ovals of tougher rock, etched and ridged and sculpted into the surface of the stone.

Diagrams explaining sedimentary rocks show beautiful neat layers of sand, laid out horizontally, but more sandstone is laid down in river deltas where the sand is moved, sorted, shoved and pushed before it is buried, and there are few neat horizontal layers.

Washout, hawkesbury sandstone, West Head Road, KCNP

The sand may have come from Broken Hill originally, it may well have made a stop or two along the way, but it has been around Sydney for 200 million years.  Roadside cuttings around Sydney reveal all sorts of sand banks and washouts in the ancient deltas, where a wandering river has passed through the sand, leaching and sifting and sorting.  The sand left behind in the old stream beds is purer than usual, lower in clays and iron.

This gives us a sandstone which is more strongly bonded, with less clay to weaken and give way.  A filled river bed of pure sand makes a fine hard rock, smooth on the surface, free of the ironstone contortions that may be seen in rocks close by.  The Eora people of the Sydney region knew this good sandstone when they saw it, just as a modern artist recognises a good canvas.  They made good use of it for their rock engravings, all over Sydney.

Inner North Head and Old Man's Hat: the joints make the vertical surfaces

Sedimentary rock is full of joints, vertical splits that cleave the large beds into smaller blocks, often running for hundreds of metres, slicing down through the geological millennia.  These joints, combined with softer and tougher beds, help shape the scenery in sandstone country.  On a small scale, joints let water into the stone, carrying minerals in, and carrying minerals out.  On a large scale, the effects of the joints can be quite breath-taking, for most of our valleys started as trickles of water following a jointing pattern.

A thin layer of resistant sandstone stands up to the forces of the weather.  Below it, softer beds may fret and wear away, undercutting the resistant bed and leaving a vertical drop for a waterfall.  When the decay reaches a joint, the blocks above will come crashing down, leaving vertical cliffs, and fresh rock for the weathering process to start on, all over again.

When there are several long-lasting beds at different levels, each one may act like a small waterfall, producing a tumbling cascade of toughened terraces and gentle spray-covered slopes.  In this case, the horizontal toughening has more influence than the vertical weakening of the joints.

Honeycomb weathering used to be blamed on sea spray soaking into rocks.  People thought that when the spray dried, salt crystals formed, and sand grains were wedged off, one by one.  Yet we find honeycomb weathering many kilometres away from the sea, and the salt spray would be less likely to get into the deepest hollows where the rock is most actively breaking down.

Cross-bedding and honeycomb weathering.

A better explanation sees moisture gathering in the hollows, and drawing soluble salts out of the rock, carrying them to the surface inside the hollows, where salt crystals fret the grains away.  But however it is caused, honeycomb weathering offers us patterns of delicate stone filigree, dancing over the surface of sandstone under sheltered overhangs, either of durable and resistant iron-rich sandstone, or the equally durable pure-sand form of the stone.

Plants and lichens dig into the surface of even the toughest sandstone, ripping the sand grains away, one by one.  The roots of gum trees and the related Angophora trees infiltrate the joints and burst the stone asunder, tumbling boulders down into gullies where floods can rush over them, wearing the stone back to sandstone again.  Through it all, the silica grains, those tiny rounded pieces of quartz, roll through the eons.  They are chemically unchanged and physically constant, shuttling their way between sand and sandstone.

Sooner or later, those sand grains that have fretted away will settle in water somewhere.  If these sand beds are buried deeply enough, the sand may melt and form granite, or it may form sandstone again.  Either way, it ensures that the intelligent beings of the planet earth, a hundred million years from now, will be able to enjoy the same wild sandstone shapes we find today.

Walking from Bondi to Watson's Bay.

Looking north on the outside of North Head, early morning.

Looking north on the outside of North Head, later in the day.

The Royal Botanic Gardens and climate change

We had to get to the Australian Museum a few weeks back, but the night was warm and we had some time to spare, so we took the scenic route.  From the ferry, we strolled around the harbour's edge to the Opera House, and on through into the Royal Botanic Gardens.  It took us a little longer, but we knew in advance that it would be worthwhile.  It always is, and not just because my wife and I both took our first degree in botany.

It is suffering right now, from one of the effects of climate change, but I will come to that in a moment.

Sydney's Gardens were founded in 1816.  They aren't the oldest in the world, for Padua, Paris, Edinburgh, Cambridge, Rio de Janeiro and Munich are all older, but few gardens could have such a fine setting.  Certainly the greatest of them all, Kew, has less to offer in the way of vistas.

It was probably fitting that Australia should establish Botanic Gardens so early, since so much of the history of white exploration and settlement was tied up with botanists and naturalists.  Not only was there Sir Joseph Banks, who sailed with Cook to Botany Bay, but Robert Brown (who told physicists about what we now call ‘Brownian motion’, and who also told biologists about the cell nucleus), Allan Cunningham, and any number of other botanists who spent time in the young colony: you can find traces of some of them in the gardens.  The tradition was later to lead Charles Darwin, T. H. Huxley to our shores, and the naturalists are still coming, even today.

At first, the gardens were seen as little more than a glorified and official vegetable garden, but slowly the plant collection developed.  The name of the water near the gardens is a reminder of this earlier role, as it is still called Farm Cove.  Six months after the first settlement, there were ‘nine acres in corn’ at the first farm, but the soil was poor, and the crop was a failure, so agriculture moved elsewhere, and the area became a centre for acclimatising new plants from overseas.

If you visit the Gardens and find a poor and unkempt looking garden bed, you are looking at a reconstruction of this first ‘farm’, but that was soon displaced by other activities.  People who wanted to grow oaks to remind them of ‘home’ could obtain acorns there, and those with damp patches on their farms could get bamboo plants.  By 1816, it had become more of a plant collection, and by 1825, there were more than 3000 plant species in the collection.  Many of our worst modern plant pests came into the country this way.

Even so, Allan Cunningham, whose tomb is to be found in the gardens, still referred to it slightingly in 1838 as the ‘Government cabbage-garden’.  The science of botany had come to take second place to horticulture, with convicts being trained in practical farming there.  The gardens declined until 1848, when Charles Moore, a trained botanist, started a 48-year reign as Director of the Gardens, and from then on, they were to be truly Botanic Gardens, as well as being the home of the National Herbarium.  This is a research collection of dried plant specimens, used in the identification of unknown species.

Moore's successor, Joseph Maiden, was also a botanist, and it showed: one of Maiden's daughters was actually named Acacia!  This is the scientific name of what we plebs call a ‘wattle’, and I have this theory about the family sitting around, asking each other, ‘What'll we call her, what'll we call her?’  Well, it's only a working theory . . .

Botanic or Botanical Gardens?  Most Sydneysiders call them the ‘Botanical Gardens’, so I asked a friend who works there, and I was told that ‘botanic’ is the old-fashioned adjective which is part of their official name.  The gardens are indeed ‘Botanical Gardens’, but not in formal matters, it seems.  Still, Sydney people aren't all that formal at the best of times.  Even so, to most people there is only the one ‘Botanical Gardens’, and that is the one at Farm Cove, just to the east of the city.  As you will read in the next paragraph, we actually have three official ‘Botanical Gardens’.  I will say more about the other two branches of ‘The Gardens’ some other time.

Entry to the gardens is free to all.  There may be an entry fee for one or two spectacular temporary displays, but it is well worth paying to see the contents of these.  On the other hand, if you are in a hurry or on a tight budget, there is a great deal more to be seen for free, out of doors, including more than a hundred bird species: you can hope to see at least twenty on any given day.

Sadly, you will also see evidence of climate change there, and two days ago, I went there to record a tidal incursion. The highest "king tide" of the year comes when the planet is closest to the Sun, which happens on January 2. On January 3 this year, there was a high tide in Sydney of 2.07 metres, and the following day, when I was there, it was 2.05 metres.

Along Farm Cove, there is a sandstone wall to stop waves breaking in, and at the bottom, there are drain holes to let rain water out, but if the tide is high enough, the sea comes in. The wall is 86 cm: remember that number.

Here is what I found:

Now just to show how bad it might have been, here is some wave action at the western end, near the Sydney Opera House (or for Sydneysiders, near Man o' War Steps).

The wall is much higher there, but it was easily overtopped. Given the right wind, this would have happened all along. Now here is what I photographed the day before, when the tide was 2.07 metres: this was at North Harbour Reserve, where I have played for 70 years, and I have asked old people, when I was young, about its history.

In the 1930s, the local civic fathers saw fit to "reclaim" a former bay to make North Harbour Reserve. They built a seawall, higher than the highest tide, and pumped in mud to make a level playing field. Some years ago, as the sea started running in, they raised the sea wall and topped it with a path. Well, that defence is failing.

Our local champion of scientific idiocy, Tony Abbott, trumpeted overseas that he had looked at local historical photos of the area, and could find no evidence of climate change.

I have lived and played around North Harbour for 70 years, and I rather think this counts as evidence. That's a king tide that could easily have been 15 cm higher, if there had been a sou'easter blowing: the old men told me all about that happening, and floating one boatshed away. We got off lucky, this time, because the weather was mild.

In 1957, when I was a teenager, a super-high tide at our standard spot for the harbour (Fort Denison) was 6 feet 1 inch, or 185 cm: now, 60 years on, it is 22 cm higher. Two days ago, the CSIRO published estimates that by the end of this century, within the likely lifetime of my grandchildren, tides will be between 45 cm and 88 cm higher than now.

Those tides will be unstoppable, all around the world, and if the upper level is reached, that increase will overtop the highest point of the Gardens' stone wall by 2 cm. Seawater will extend well into the Gardens, killing and ruining our heritage.

One wonders if our do-nothing, look-at-me polly will seek funding to raise both the seawall and the park surface, or if he will just scream "fake news!".

Please share this link: we might manage to get Nero to stop fiddling ...

New Year in Sydney

First, here are some samples of a Sydney New Year's Eve, taken from expensive seats on Pinchgut, two years back. This year, we and our standard NYE friends will dine at a quiet restaurant away from the lowing herd, then walk back to our house to see the New Year in, on a north-facing balcony, looking away from the glows in the sky. After almost 50 years of harbour fireworks (the first we saw were in 1970), we don't like the discomfort and the heaving crowds.

Beforehand

Things happened to amuse the waiting crowds. Remember the bridge, because it plays a role.

The sun set, but it wasn't 9 pm yet.

Finally, the show began. Look for the bridge and the Opera House.

Look for the bridge and the Opera House. These are our tribal icons.

Among the guests on Pinchgut were two Scots couples who come out each year for the fireworks on the harbour. I fear they may have had to find a new vantage point this year, as the restaurant on the island seems to have disappeared.  Our Australian celebration of New Year's Day owes a lot to our Scots heritage.  Perhaps I am a biased observer.  As my surname implies, my ancestors were Scots.  My family has been here since early colonial days, but we still keep many of the old traditions intact.

Even in my generation, there has always been at least one piper in the family to welcome in the New Year with a skirl, and the bagpipe remains my favourite solo instrument, for I spent my earliest New Year's Eves, standing directly beneath my father's chanter (that's the lowest pipe, the one you twiddle on), taking in the sound and the smell of the pipes.

Perhaps I will learn to play the pipes when I retire.  I will be in good company if I do, for I know of just the pipe band for me, made up entirely of old and retired ‘Scots’, most with broad Australian accents.  Some traditions die hard, even under an Antipodean sun.

Others may celebrate their New Year's Day by nothing more than a day at the beach, or around a suburban backyard pool.  Still, some hardy traditional types will spend the day at a Highland Gathering, engaging in all sorts of strange activities like tossing the caber and wild dancing to pipes that serve to remind them of the hangover they still bear from the night before.

Traditionally, anybody can be a Scot on that day.  My father knew a champion piper called Colin Campbell who was, as it happens, one of the original Australians.  In those days, whites would stress further that Colin was a ‘full-blooded aboriginal’.  Be that as it may, he would appear each year in the New Year's Day piping competitions to play his own spirited rendition of ‘A man's a man for a'that’, and often to take prizes for his playing.  Those who know their Burns, of course, will see Colin's point . . .

But Sydney has always had its unusual Scots.  A hundred years ago, a Chinese merchant of Sydney, one Quong Tart by name, was popularly known to one and all as ‘Quong Tartan’.  He came to the Australian goldfields as a small boy, and was taught English by Scots people, so his accent was well suited to his nickname.  Historical accounts mention that he was an accomplished reciter of the poems of Robbie Burns, including, I imagine, ‘A man's a man for a'that’.

One of the things which strikes tourists about Sydney is the huge range of faces on the street, but this is by no means new.  Now, we call it ‘multiculturalism’, but it used to happen a hundred years ago as well.  Here is what ‘James O'Connell’ wrote in 1836, preserving his spelling:

In George street, the grand thoroughfare, the visiter is amused with the motley group of divers nations, kindreds, and tongues that he encounters.  New Holland is less exclusively the residence of convicts than the reader may have imagined.  Settlers and visiters from all portions of the globe — Spaniards, Frenchmen, Englishmen, Americans, Chinese, Malays, Kanakas or South Sea Islanders, the latter arriving in whale ships, add variety to a scene which, without them, would be varied enough.

‘O'Connell’ was an escaped convict who had clearly spent several New Year's days here before he escaped to Ponape (Pohnpei) in what was then the Caroline Islands, and later to the United States, but let us stay with the present, for now.

Other Australians will spend New Year's Day in the bush.  No, not in A bush, but in the bush.  That is, in what other lands might call a wilderness, a forest, a jungle, or even a heath.  To us, these are all one and the same: they are all ‘bush’.  Where other nations go hiking or back-packing, we go bush-walking.  Last century, we never had highwaymen, but we always had our bushrangers.  We took the word "bushranger" from the Americans, who used it to mean anybody who roamed freely through the forests, but it soon took on the meaning of an armed robber.

‘Bush’ can also mean anything rural, not of the city, as in ‘the city or the bush’, or as in a classic ribald poem, ‘The Bastard from the Bush’, but mainly it refers to those patches of native Australian vegetation which are to be found, even in the middle of a city of nearly four million people like Sydney.

New Year's Day will be a hot and listless high summer day, so the sensible thing to do is to find a shady spot beside a creek, to swim a bit, to eat a bit, to drink a bit, to relax and enjoy the quietness.  One of the joys of Sydney is that you can find clean cool water in a quiet gully, within an hour of the very centre of the city.  The most preferred housing sites have a harbour view, closely followed by those looking over, and surrounded by, bush.

Of course, this can also a drawback, for those patches of bush can flare up into cruel bushfires, but that is something most people prefer not to think about on New Year's Day.  It is high summer, there is cricket on TV, beer in the fridge, and tomorrow will be a time to relax, at least for now.

I might just spend a few days in the bush. After all, ours is an evolving culture.

Still, bliadhna mhath ur.

Frogging

This went out originally as an ABC Radio National broadcast on Ockham's Razor. It has been edited to disguise locations.

It is a warm and moonless Saturday night.  It is raining, the cloud is down so low on the headland that it qualifies legally and scientifically as mist, and I am wandering around in the dark through dense heathland, half a kilometre from home, with the rain soaking through my broad-brimmed hat, and running down my neck.  Every so often, I stop and shout ‘FROG!’ as loudly as I can.  Then I raise my dripping hat to hear if anything answers.

It is probably fair to ask whether these are the actions of a sane man.  I say they are, but then I know what I am doing.  Or that is my story, at any rate, and I would like to stress here my non-membership of that strange breed, the compulsive froggers, people who sometimes care more for frogs and toads than they do for humans.

I know that I retain my sense of proportion, my sanity, for out there, alone in the dark, I am still rational enough to ask myself what I am doing there.

I am on a headland near Sydney Harbour, in a large patch of bush where there are three, or possibly four species of frog.  After steady rain, there will be equally steady seepage out of the sandy soil for some weeks, and the frogs have a chance to rebuild their numbers.  They gather near the trickling water, they call, and they mate.  Their tadpoles will hatch a few days later and rush through a hurried childhood into premature adolescence, before they join their parents on the drying land.

As a child, I collected tadpoles once or twice in a glass jar and brought them home, but I never succeeded in growing any up to be frogs.  As a young adult, I maintained a genial interest in frogs.  I learned to feed the tadpoles on lettuce, to get them to the adult stage.  Most importantly, I learned to provide them with a rock to rest on, a way out of the water.  Emergent frogs have lungs, not gills, and they will drown if they cannot scramble out.

Many years ago, as a young biology teacher, I acquired by devious means a lockable glass-fronted cupboard, designed for chemical storage.  I bolted it to a corridor wall where passing students could look in.  I bought a narrow glass tank and went through a number of frog-breeding cycles over several years, but I was still not a compulsive frogger.  I just thought it was good for students to have a small ‘zoo’ to look at.  Tadpoles and frogs were a major part of what happened there, along with assorted invertebrates and static demonstrations, but I was definitely not a compulsive frogger.

Later, I moved house, and we soon found that frogs had joined us in our garden.  We got up one rainy morning to find that we had a frothy mass of frog eggs in plastic bowl that lay abandoned in the garden.  Delighted, I dug a small pond, and transferred the eggs across.  Soon after, when I had to build some new stairs and a landing into the backyard, I constructed a much larger pond in the wasted space underneath the stairs.  Friends thought this a little eccentric, but I knew I was still not a compulsive frogger.  Even the friends could see that, when I explained it to them.

Some years later still, I found myself working in a museum, and I was cajoled into working on a project called Frog Watch, that involved both frogs and computers.  I was involved more as a writer and computer person, though I found myself getting more involved in froggy things.  But still I resisted the temptation to become a compulsive frogger.

I met quite a few compulsive froggers while I was there.  One of them noticed a small population of tadpoles sharing a pool with some mosquito fish.  This surprised him, for mosquito fishes will attack most tadpoles, and eat them, working up from the tail.  Most people would have passed on to other things, but this frogger thought about it, and concluded that the tadpole must taste rather awful.  A true man of science, he tried eating several of the raw tadpoles.  They tasted vile, a discovery which may have waited forever, but for the dedicated commitment of this compulsive frogger.

I met a fellow worker, who kept several pet frogs in a tank in his office, where they responded every time his phone rang.  Later, I edited a frog book for another colleague, who kept a one-eyed tree frog in his workshop (it lost the other eye when a truck ran over it, but my colleague nursed it back to health).  I knew I was still not a compulsive frogger, not by any of the rational standards that I could construct.

Pseudophryne australis, otherwise the Sydney red-crowned toadlet.
CC BY-SA 3.0, 
https://commons.wikimedia.org/w/index.php?curid=1185340

Then I moved house again.  Soon I started to notice the several frogs living around my house.  I bought tapes to identify them (you ‘earball’ frogs rather than eyeballing them), and I started to learn how to provoke certain species to call.  Then one day I found a small frog in my front yard, did a quick double-take.

With delight, I realised that the seepage drain near my front gate was home to a member of an endangered species, a Sydney Red-crowned Toadlet.  I was still not a compulsive frogger, but now I was distinctly interested.

Since then, I have been trying to map the frog's distribution in the local area by going out in wet weather and listening for the toadlet's distinctive call.  Somebody in Canberra told me once that the Corroboree Frog, another member of the same genus, will answer if a male human voice bellows ‘FROG!’ nearby.  Testing that theory is what leads me out into the wilderness on damp still nights, shouting in the dark.  That and finding out just how healthy the local population is, but I am still not a compulsive frogger.

My little toadlet lives in some two hundred pockets of land around Sydney.  In all likelihood, each population carries different genes, but there is no flow of genes between the different localities.  Each group is an isolated remnant.  If any group dies, it will not be replaced by new colonists moving in, for they cannot swim over the salt water of the harbour.  There is no bridge for them to use, and pioneers cannot hop over the 5 kilometres of settled ground to get here from the next pocket.

The toadlet's distinctive  underbelly.
By Tnarg 12345 at the English language Wikipedia, CC BY-SA
3.0, https://commons.wikimedia.org/w/index.php?curid=2652554

If any isolated group dies out, its small part of the genetic diversity dies with it.  The special genes that they alone may have are no longer available to the population as a whole.

It is a simple enough principle: even the ancient Romans understood it, when they coined the phrase ‘Divide et impera’ — divide and rule.  It is a cold implacable logical law, and its operation may one day wipe out all of the toadlets.

But why should we worry about one little frog, when there are hundreds of other species in Australia?  Many years ago, Paul Ehrlich taught us that we should think of an ecosystem as rather like an aeroplane which can lose a few bits and still fly.

I prefer to see an ecosystem as a steel bridge.  You can take one rivet away from a bridge, and nothing will happen.  You can remove another rivet, and the bridge will be as steady as ever.  You may even take some more, and still do no harm.  But somewhere along the way, you will take out one rivet too many, and the bridge will come tumbling down.  Ecosystems are robust, they can manage without some of the key species, but sooner or later, they start falling apart.

Biodiversity in a species works the same way.  Eliminate a few unusual genes, and no harm will arise, not yet.  Take a few more rare genes away, and there will still be no problem.  Sooner or later, though, some other change will mean that one of those eliminated genes will be needed.  By then, it won't be there, because the gene's minders have died, and the gene has died with them.  All over Australia, the frogs and toads are reminding us, calling ‘rivet, rivet’, but nobody cares, for the frogs' bridge is still standing.  It sags a bit, it may sway perilously from time to time, but it is still there.

It is a warm and moonless Saturday night.  It is raining, the cloud is down so low on the headland that it qualifies legally and scientifically as mist, and I am wandering around in the dark through dense heathland, half a kilometre from home, with the rain soaking through my broad-brimmed hat, and running down my neck.  Every so often, I stop and shout ‘FROG!’ as loudly as I can.  Then I raise my dripping hat to hear if anything answers.

I know now why I am there in the dripping mist.  I am still not a compulsive frogger, but I think I understand them now.

Food preservation

Here's a small sample from Not Your Usual Science, which is now finished, but getting a last polish. That will take a while, as it ended up at 460,000 words. It will be out on Kindle in a month or two.

The illustrations are from a recent visit to Sri Lanka, where I saw fish being sun-dried.

Negombo beach, tuna.

Nobody ever sat down and thought “today, I will invent technology and change society”. It was more likely to be a matter of certain aspects of technology emerging, after which people used the new ideas, and only realised later that they had changed their society. Even more likely, they found a new way, used it, and changed their habits, which in turn changed society.

Before the development of agriculture, people had to live a nomadic life, moving after the food, following the seasons. Once they had ways of growing food near a permanent home, they could settle in one place, but then they needed ways to preserve and/or store food, to stop it going bad.

A closer view of the tuna

The process would have begun slowly, because even nomads knew how to smoke meat over a slow fire, or use sunlight to make beef jerky. Fish could also be dried or smoked. Before people knew about germs, salting was a good way to stop germs growing on meat.

Water can flow out of living cells and it can also flow back in through the cell membranes. High salt concentrations outside a cell stop water going back in, so any microbes in salted food soon dry up and die. When beef or other meat is dried, the salts in the meat are left behind, and once again, the salt levels stop bacteria and fungi from growing. (If you want to know what is going on here, the key word is osmosis, but right now, we are discussing history.)

Bees have used the drying method for millions of years, collecting nectar and fanning it to evaporate off most of the water, changing the nectar to honey. Spores and germs that fall into the honey simply cannot grow. When sugar cane is crushed, the juice is boiled and this concentrates the solution to stop any fungi or bacteria surviving in it.

All sorts of fish are dried.

By good luck, heating the cane juice also destroys a natural enzyme in the sugar cane which breaks the sucrose molecule down into simpler sugar molecules which are less useful, and the whole sugar industry depends on destroying this enzyme.

Islamic societies around the Mediterranean followed to a greater or lesser extent the teaching in the Quran that drinking alcohol was wrong, but even pious Muslims still liked cooling drinks. Highly concentrated fruit juice and sugar would keep forever, as nothing could live in it, but this cordial could be mixed with cool water to make a pleasant drink.

They are mainly carried inland and sold. Without fish, the
inland folk would have an iodine deficiency and goitre.
In a very real sense, the population depends on dried fish.

When the Egyptians preserved dead bodies, they used a similar method, but they replaced ordinary salt with natron, a mixture of sodium carbonate and bicarbonate which, as we have seen, was also used in glass making. The mummies would have tasted better with salt, but as nobody planned to eat them, natron was fine.

All the same, it would be reasonable to suspect that the Egyptians knew about salting meat before they made mummies, which would mean they must have started salting meat at least 4500 years ago.

Whatever method is used, preservation either sets out to kill the food-spoiling microbes, or to slow them down, making the food last longer. Warming up food makes a perfect environment for germs to multiply, and “food poisoning” often begins with warmed-up food being set aside and then heated again.

Geoffrey Chaucer was an English poet and scholar who died in 1400, as the Middle Ages came to an end, but he knew all about this danger. In his Canterbury Tales, Chaucer has a character accuse a cook of ignoring this risk. The Jack of Dover mentioned here was almost certainly a pie of some sort:

And many a Jakke of Dovere hastow soold,
That hath been twies hoot and twies coold.

 In more modern (but similar) language, this says:

And many a Jack of Dover hast thou sold,
That had been twice hot and twice cold.

Refrigeration is a good way of slowing down germs, but as Chaucer knew, more than 600 years ago, the cook’s habit of re-warming food made it potentially deadly. Unlike Chaucer, we realise that repeated warming of food can increase the number of bacteria to dangerous levels, but even without knowing about germs, Chaucer knew that reheated food was dangerous.

We can look at a food preservation method today and see the science which lies behind it, but each of the methods must have been originally discovered by chance, perhaps when an animal drowned in a brine pond, and was later found, free of rot.

Food left too long over a low fire may have been dried or smoked, wheat and barley stored in pots in hot dry places stayed dry and undamaged, and so on. Freezing of dead animals caught in a snowdrift may have preserved their meat, but looking into this actually killed one scientist, Francis Bacon, also known as Lord Verulam:

Mr Hobbs told me that the cause of his Lordship’s death was trying an Experiment … it came into my Lord’s thoughts, why flesh might not be preserved in snow, as in Salt. They … bought a Hen, and made the woman exenterate it, and then stuffed the body with Snow, and my Lord did help doe it himselfe. The snow so chilled him that he fell immediately ill … they put him into a good bed, warmed with a Panne, but it was a damp bed that had not been layn-in in about a yeare before, which gave him such a colde that in 2 or 3 dayes … he dyed of Suffocation.
— John Aubrey, discussing Francis Bacon (1561 – 1626), Aubrey’s Brief Lives, 179.

Whichever way the food was preserved, even without knowing anything about the spores, bacteria or fungi, humans stopped their food spoiling. The result was that people were able to live through bad seasons or times when there was no food to be had. They were also able to store food such as turnips or hay to keep animals alive, and dried foods were light enough to carry on long journeys.

Unfortunately, some preservation methods also destroyed any vitamins that might have been in the foods. Sailors and other travellers who tried to live on salt meat and ship’s biscuit (a very dry sort of bread) risked developing ‘disease’, as scurvy used to be called. On short voyages, the passengers and crew had enough vitamin reserves in their bodies to stay fairly healthy, but as voyages grew longer, people began to sicken, or even die, killed by the preserved food they thought was keeping them alive.

Pickling with a mixture of salt and vinegar can stop vegetables spoiling. Salt does not destroy vitamin C, the cure for scurvy. Salt meat has no vitamin C because the original meat had none, but pickled cabbage, sauerkraut, still has most of the vitamin C found in the original cabbage. Lime juice was boiled to a concentrated germ-resistant syrup. That usually kept some of its vitamin C, so long as the lime juice had not been boiled in copper pots. Copper surfaces are very good at destroying the vitamin.

Preserved foods allowed Europeans to discover the whole world and then dominate it. It was a mixed blessing, when you consider how they treated those they dominated!

Bushfire backgrounder

Bushfires are a part of high summer in Australia. In winter each year, Australians carry out control burns, small fires aimed at reducing the amount of standing fuel. These may help to contain the fires or stop them, but given the wrong weather, no amount of control burning can stop fires happening somewhere. The science is against any other outcome.

A note first about terms: in Australian English, ‘bush’ is what others might call forest, heath or scrub. The term was brought to Australia by early settlers who had previously lived and worked in North America, so this quintessentially Australian term is in fact an early American import! A ‘bushfire’ is a fire running wild in the bush. 

Many botanists in the past have been forced to change their research to ‘bushfire regeneration’ after their plots were burned out, and the cost of fires has meant that there has been a great deal of research on the topic.

First, let us consider the biology of bushfire in Australia. Fire is a natural part of the bush cycle, so the natural environment should survive fairly well, just so long as there is no heavy rain, too soon afterwards. That is why the fire fighters will concentrate on saving property and lives.

They will fight fire with fire, knowing that what they burn deliberately will grow back again, refreshed by the flames. Australia’s bush, after all, lived with fire for many millions of years, long before humans came here. The bush will grow back after the fires have done their worst.

Next, let us consider the geology and geography of urban Sydney bushfires. When the first Europeans reached Australia in 1788, they settled in what is now Sydney, either on flat land near the sea or on the ridges.

Sydney sits on a bed of sandstone, two to three hundred metres thick, with joints running north-south and east-west. It was laid down in a Triassic delta, rather like Bangladesh today, with a huge river braiding back and forth, washing out the finest minerals, the clay and other mineral-rich sediments, and leaving just the quartz grains behind. The grains were rounded, and had probably been in an earlier sandstone somewhere else, but they settled where Sydney is now, almost 200 million years ago, waiting to play their part in shaping modern Sydney.

Some of the sandstone beds are better bonded than the others within this ‘Hawkesbury sandstone’, but they are otherwise pretty much the same, right through the deposit. (Hawkesbury, in case you are wondering, was a minor 18th century English politician who had a local river named after him. The stone was later named after the river.)

In the last Ice Age, the sea level around Australia was much lower, due to all the water tied up in the northern glaciers. Then, today’s Sydney Harbour was a river valley, shaped by the jointing pattern in the sandstone. Joints, planes of weakness in the stone, were eroded into crevices which became valleys, with the more resistant sandstone forming ridges. Later, the sea level rose, creating a ‘drowned river valley’ with a characteristic fern leaf shape, the modern Sydney Harbour. A few of the higher ridges have a shale capping which offered rather better soil than the sand which derives from sandstone.

The first whites settled on the coast, then headed (a) for the flat land of the ridges, where roads were easier to build, and (b) for the richer soil on the shale-capped ridges. First, they built small farms and market gardens, then roads were built to service these, and soon the residences followed, as a young city grew. Down in the valleys, close to the sea, the bush was left alone. It was too hard to build roads down to there, and so people left it alone. Even today, much of the valley bush is preserved, with homes sitting on the ridges above: a sure recipe for trouble, because heat and flames rise.

Fuel builds up in the bush over a period of years. Gum trees shed their bark, branches and leaves, smaller shrubs in the under-storey die and are replaced by others, and after a few years of recovery, the lowest three metres or so is a closely packed mass of dead and drying twigs. Until they break and fall, these pieces of finely divided wood rot very little in the dry bush, and even on the forest floor, rotting is a slow business, for the sandy soil drains fast after rain. Heath regenerates fast.

Some of them can be ready to burn again, just six months after a major fire. Other areas can take ten to twenty years to be ready for a major burn. As a general rule, after 40 or 50 years, any area at all will be ready to sustain a ‘blow-up fire’.

Now for the physics of bushfires in Australia. When any fire starts, it begins very slowly. It takes time to develop from a maker of smoky wisps into a maker of misery. The dangerous fire is one that roars and gusts through the tree tops, the crowns of the trees, a firestorm traveling at 50 kilometres an hour or more, leaping ahead of itself, and destroying all in its path.

Crowning fires can cross 400 metres of open water, as the sparks and burning rubbish fly up in the roaring flames, and then tumble down on the other side. Any footage you see on your local TV will be of these crowning wildfires.

You will see flames gouting 30 metres or more into the air, searing the upper branches of gum trees, leaping across the fire breaks, and almost impossible to control until the weather improves.

Now let us look at the question of weather and bushfires. The weather is the last factor in the bushfire equation. At the moment, we have hot dry nor-westers, gusting at up to 50 knots, pushing the fires downhill as well as up. Usually, a fire front can be beaten as it crests a ridge.

Fires go fast uphill and slow downhill, but they do run downhill. On the forward side of any advancing fire, you will find a wind blowing towards the flames at the front of the fire. If you can set small fires on the far side of a ridge, they will gather strength and rush up, sucked in by the fire wind from the blaze on the other side, until the small fires meet the major fire coming the other way.

In this style of fire-fighting, the major fire limps over the ridge, only to find that most of the fuel in its path has already been burned. Starved, it falters like a wounded beast, and puny men and women rush in to attack it with sprays and hoses. But with high winds, this ploy is too dangerous to attempt, as the fire lighters in its path could easily be over-run, as it leaps over the fire break they have just made.

Within hours of the fire, the seeds will be dropping from the woody fruits of the she-oaks, Hakeas and Banksias, and the trunks and underground stems of other plants will already be starting to shoot. In three weeks, there will be green all over the bush. In time, the bush will recover, and so will the animals. The homes can be rebuilt, and lives, so long as they have not been lost, will go on. It is all part of the natural cycle. The animals will take longer, but some will survive, and others will move in from unburnt areas, but recovery is a slow natural cycle.

Inventing writing

Another sample from Not Your Usual Science. Be patient... I got side-tracked to do an essay on poisons (one of my favourite topics) that looks like turning into a book.

So since we are talking about writing, there were a few conditions that would need to be met before writing caught on. As a rule, nomads would not wish to make or carry around records, especially when they were written on heavy clay tablets. So people probably needed something to write on, something to write with, and a useful place where the written records could be kept. Inscribed stones might appear, but unless there were other uses, the whole writing thing might be a bit of a flash in the pan.

The Sumerians explained the invention of writing with a sort of fairy tale about a messenger who was so tired when he reached the court of a distant ruler that he could not deliver his message from the king of Uruk. Hearing this, the Sumerian king took a piece of clay, flattened it, and wrote a message on it.

That story has a few sizable holes in it. How would the person receiving the message know what the symbols meant? Then again, what can we expect in a tale about events that happened so long ago, especially when it was probably not written down?

Hieroglyphs. [Christine Macinnis]

The Egyptians said the god Thoth (the scribe and historian of the gods) invented hieroglyphs; the Sumerians either credited the unnamed king who wrote to Uruk — or the god Enlil. The Assyrians and Babylonians said the god Nabu was the inventor, while the Mayans said they owed their writing system to the supreme deity Itzamna who was a shaman, a sorcerer, and creator of the world.

More plausibly, Chinese tradition says writing was invented by a sage called Ts’ang Chieh, a minister to the legendary Huang Ti (the Yellow Emperor).

How many of these can you "read"?

Some writing used characters to represent syllables, other writing systems used a symbol just to mean a letter-sound (as we do in English), while still others used a symbol to mean a word or idea, as happens in Chinese.

These word/idea symbols are called ideograms or logograms (meaning each symbol is an idea), and they can mean the same thing in different languages, rather like the signs in airports or the numeral 5. Just to confuse things, some of those airport signs are also called pictograms, because they are pictures of what they represent.

Then again, Egyptian hieroglyphs are a mixture of alphabetic characters and ideograms, with a few extra symbols to clarify the meaning. Few writing systems were designed from scratch: they just grew, a bit like English spelling!

The Sumerians lived in what is now southern Iraq. Ignoring the myth quoted above, their writing probably started with marks on clay that Sumerian accountants used around 3300 or 3200 BCE to record numbers of livestock and stores of grain, the sorts of records societies need, once they start farming. Over about 500 years, the symbols became more abstract, allowing ideas to be written down as well.

Egyptian hieroglyphs (literally, the word means ‘priestly writing’) are unlike Sumerian cuneiform. They probably developed separately, but maybe the Egyptians got the basic idea of marks to represent language from other people. The Harappan script from the Indus valley in what is now Pakistan and western India, seems to be another independent growth, though nobody has learned to read it yet. The civilisation which established it collapsed in about 1900 BCE, so the script did not develop further.

The oldest alphabets that we know about seem to have emerged in Egypt around 1800 BCE. They were developed by people speaking a Semitic language, and the writing only covered consonants. These variants later gave rise to several other systems: a Proto-Canaanite alphabet at around 1400 BCE and a South Arabian alphabet, some 200 years later. There were others, but we will stay with those examples.

The Phoenicians adopted the Proto-Canaanite alphabet which later became both Aramaic and Greek, then through Greek, inspired other alphabets used in Anatolia and Italy, and so gave us the Latin alphabet, which became our modern alphabet. Aramaic may have inspired some Indian scripts, and certainly became the Hebrew and Arabic scripts. Greek and Latin inspired Norse runes and also the Gothic and Cyrillic alphabets.

The Rosetta Stone solved a lot of puzzles.

Now the way was open for poetry, literature, history, philosophy, mathematics, recipes, technical information, tax, weather and astronomical records, religious teachings and more to be written down and passed from one generation to another, without the need for story-teller, whose main role was to memorise everything.

Just occasionally, we can get lucky, but most ancient systems are only ‘cracked’ by intensive work. Carved in 196 BCE, the Rosetta stone was found in 1799 by French soldiers fighting in the Napoleonic Wars in Egypt. The inscriptions all said the same thing, but in Greek, in Egyptian demotic script, and in hieroglyphics. In other words, for the first time, the mysterious hieroglyphics could be compared with a translation.

The content is fairly boring, a list of taxes repealed by Ptolemy V, but the use of three languages made the stone very exciting. When the French were defeated, it was handed over to the British, and placed on display at the British Museum in 1802.

The Rosetta Stone was described by its original French finders as ‘une pierre de granite noir’, a stone of black granite, but this was not a geologist’s granite. This term ‘black granite’, conferred in less geologically rigorous times, was applied 200 years ago by Egyptologists to a dark, fine-grained stone from Aswan. The British have always called the stone basalt, since they gained possession of it during the Napoleonic wars. Neither description is correct.

Recent cleaning and a careful examination has shown that the stone was probably sourced from Ptolemaic quarries to the south of Aswan. Probably nobody cared much what the stone was, as the important question was the text, not the material it was inscribed on.

From a geological viewpoint, though, it is neither a basalt nor a granite, but a fine-grained granodiorite, perhaps modified by metamorphic and/or metasomatic processes. For most purposes, we can think of it as a granodiorite, but in chemical terms, say the researchers who have looked at it, the stone is more like tonalite.

Granodiorite has quartz and plagioclase, but it also contains biotite and hornblende, and it is typically darker than granite. All the same, it is hard to see how it could be mistaken for basalt, but the secret to the issue lies in the reference to recent cleaning.

The confusion arose because the stone has been covered for many years with black carnauba wax, remnants of printer’s ink, used to obtain contact-prints of the inscriptions, finger grease and dirt, with white paint in the incised lettering to make it stand out.

When the stone was being cleaned in 1998, it became apparent that the stone was not basalt at all. Work based on petrographic examination and analysis of a fragment from the Rosetta Stone showed conclusively that it is a granodiorite. To be precise, the Rosetta Stone is made of a granodiorite that has probably been exposed to some extra heating. It is not basalt, but it should not be taken for granite, either.

The First Koel

Canowie Brook, Budawang Ranges.

I have been busy, putting the final touches on (working title) Survivor Kids, a book scheduled to hit the shelves in February 2020. It's about how to survive in the wilds, places like the above, how not to get lost, stuff like that. I put the finishing touches on it last night, and now I will slowly and carefully start to polish it. And now, I have more time to muse, until the edits of Australian Backyard Earth Scientist begin coming back.

Sherlock Holmes would not have approved of the dog next door.  It started barking into the pre-dawn gloom, just a few nights ago.  When looking into the case known as The Hound of the Baskervilles, Mr Holmes was more interested in dogs that did not bark — as am I, come to think of it!

I had a good idea of what had provoked the dog to action, but I had to wait until last night to confirm it, when, from a deep slumber, I heard a shriek behind our house.

It was a frightful cry, very hard to describe.  The nearest I can get would be to suggest that it sounds rather like an elderly naked duchess being goosed with ice-cold tongs.  But if it is hard to describe, the meaning of the noise is crystal clear.  The koels have arrived.

In England, they write to The Times, overjoyed to report the first cuckoo of spring.  We Sydneysiders write to the Herald, rather more underjoyed about the first koel, even though it, too, is a cuckoo.  The name (it rhymes with Noel, as in ‘The First Noel’), reflects the sound of its call, described in one of my reference books as ‘koo-well’.  This description fails to convey the full flavour and savour of the bird's cry, and so I prefer the goosed duchess.  Of course, that might just be because I never did have much time for duchesses . . .

The koels fly south around the equinox or a few weeks later, coming down from Papua-New Guinea, the large lizard-shaped island that lies above the right-hand side of Australia on your maps.  Having arrived, they choose territories where they can exploit the local feathered baby-sitting facilities, just like their cuckoo relatives in other parts of the world.  Then in the wee small hours of our early spring mornings, around 3.30 or 4 am, they start their calling. This year, they seem to have arrived later than usual.

We really should not blame the koels, for they are simply staking a claim to a territory, although the resource they care most about is nesting sites for their target species.  They are too late this year, for  the noisy miners have already hatched their first brood for the year, but there will be a second sitting, a second chance, later in the year, when high summer arrives.  In a few weeks, the koels will realise that they need to play a waiting game for a while, and they will quieten down.  Maybe.  In the meantime, we will suffer fitful snoozing from false dawn to sunrise for a few weeks.

In Australian English, there are many different meanings of ‘clock’.  It can be variously a time-piece, an embroidered design on a sock, or a twelve-month prison sentence.  ‘To clock’ can be to give a punch or a blow, or it can mean to time (a horse or a runner), or it can have other lesser meanings as well.

Our koels may be Antipodean cuckoos, but nobody in their right mind would wish to make a koel clock that would bellow each quarter-hour so unmelodiously.  On the other hand, right now, most of us Antipodeans would relish the prospect of being able to clock the koels.  Hard.