Now then, here we have a fish, and to give you some idea about how it is preserved
what I'm going to do is dip it into two things which we must pretend for today
are liquid rock. And I'm first of all going to put it in this and because
this rock is nice and liquid like this I need to freeze it very quickly indeed.
Now the freezing process to accelerate it, which has got nothing at all to do
with the fossil record is using liquid nitrogen and we put it in like that,
freeze in that direction, out it goes - poor fish - then we put it into things
like that and we repeat this process, because what I'm trying to demonstrate
is how the mineral salts precipitate themselves round the fish in alternate
layers. And of course so we then have a fossilization like that - goodness me!
This is science, sort of fun! And you end up with something which on the outside
is really a pretty shapeless object. But we know, of course, that inside it there is
a fish lurking. But again if you're the fossil hunter, you might well find
something like that in a field, crack it open, and reveal a fish within. But, is
it absolutely necessary always to attack everything you find with a hammer and
chisel? Do you have to bang everything open, do you have to hurl things apart to
reveal the internal fossils? Sometimes of course you do, but there are more subtle
ways in which we can approach this particular problem. And by way of an
introduction, what we have in here is a mystery object and we've got to imagine
that this is preserved in exactly the same way as the nodules which I just
showed you there. Now, a scientific method which is very widely used is to
actually find chemicals - weak acids - which can etch away the outside layers and so
reveal the internal fish within. Now this of course has to be an incredibly
delicate process, so that when I start to do this here the amount of effervescence
- the activity which is going on like this - is very much more rapid than what we would seek to do in the laboratory. But all the times you can see
the chemical here is etching into the nodule substance - a white material on the
outside - and as it etches in in that direction, so in due course, we hope it
will reveal exactly what is there. Now I think that's going to take a minute or
two so I'll leave that just to sort of bob around like that, while you can
engage in guessing games as to what might be concealed within. Because again,
this has a real scientific purpose. What we see in this example here is precisely
what paleontologists, the people who study the fossils, use to examine
the remains of certain ancient life. Now here, I really have to keep my hands
incredibly still because we have two of the most fantastic fossils imaginable
which actually come from Australia. They're about 350 - roughly - million years
old, and it just gives you some idea - let me just pick this up, I have to work over
this one terribly slowly. It's a wonderful specimen. Because what's
happening in that tank there has been done with much more care in this fossil.
Here is the remains of the nodule, and can you see the fossil fish preserved
within it? Do you see the head here? Every bone is in place and then the scales of
the fish, the back like that, and then here all the scales are loose - perhaps
this end of the fish was beginning to rot away, do you see the way the scales
are much more disturbed, much more difficult to see? And all of this being
revealed by just the same process as we see in this area here. Delicate, very
delicate, etching by weak acids and I put that back, holding my heart still. This
other specimen I simply will not pick up, it is much too delicate -
but that skull, in fact it comes from a fossil fish, is the same age as this fish,
it's from the same deposit, and the whole of that skull has been isolated from
this constant edging away of this nodule-like material here. So there that is
almost indistinguishable from some sort of modern preparation,
that's the sort of thing which if after you've had dinner and eaten
fish perhaps, that's more or less what you see. Yet this is hundreds of millions
of years old. If I did pick that up - I won't - the jaws could open, you can see
inside its mouth. It's an absolutely startling specimen. Now I do fear that
the rate at which - ah yes, things are coming
clear! If I just turn it slowly I think you can begin to see that, yes indeed
there is not surprisingly, yet another fish about to emerge. Well we'll leave that to
fizz away in it's acid bath and within about ten minutes or so that thing will
be completely free of its encasing material. A standard technique which is
very widely used.